Because the SB is only good for 8k and Go programs
tend to have much more data than that, SB doesn't
save very much.  A fmt.Printf-based hello world program
has  360 kB text segment.  Removing SB makes the text
500 bytes (0.14%) longer.

R=ken2, r2, ken3
CC=golang-dev
https://golang.org/cl/2487042

R=rsc, brainman
CC=golang-dev
https://golang.org/cl/2543042

R=ken2
CC=golang-dev
https://golang.org/cl/2481042

R=adg
CC=golang-dev
https://golang.org/cl/2521042

or at least gather more information

R=ken2
CC=golang-dev
https://golang.org/cl/2515042

R=rsc
CC=golang-dev
https://golang.org/cl/2519042

Also change the span-dependent jump algorithm
to use fewer iterations:

* resolve forward jumps at their targets (comefrom list)
* mark jumps as small or big and only do small->big
* record whether a jump failed to be encodable

These changes mean that a function with only small
jumps can be laid out in a single iteration, and the
vast majority of functions take just two iterations.
I was seeing a maximum of 5 iterations before; the
max now is 3 and there are fewer that get even that far.

R=ken2
CC=golang-dev
https://golang.org/cl/2537041

The old code said

	if(x) {
		handle a
		return
	}
	aa = *a
	rewrite aa to make x true
	recursivecall(&aa)

The new code says

	params = copy out of a
	if(!x) {
		rewrite params to make x true
	}
	handle params

but it's hard to see that in the Rietveld diffs because
it gets confused by changes in indentation.

Avoiding the recursion makes other changes easier.

R=ken2
CC=golang-dev
https://golang.org/cl/2533041

Using explicit relocations internally, we can
represent the data for a particular symbol as
an initialized block of memory instead of a
linked list of ADATA instructions.  The real
goal here is to be able to hand off some of the
relocations to the dynamic linker when interacting
with system libraries, but a pleasant side effect is
that the memory image is much more compact
than the ADATA list, so the linkers use less memory.

R=ken2
CC=golang-dev
https://golang.org/cl/2512041

R=r
CC=golang-dev
https://golang.org/cl/2526041

R=r, r2
CC=golang-dev
https://golang.org/cl/2493043

R=adg
CC=golang-dev
https://golang.org/cl/2525042

R=r
CC=golang-dev
https://golang.org/cl/2525041

R=ken2
CC=golang-dev
https://golang.org/cl/2520042

Suggested by fango (fan.howard@gmail.com)

R=r, r2
CC=golang-dev
https://golang.org/cl/2514041

Fixes #1195.

R=rsc
CC=golang-dev
https://golang.org/cl/2504043

R=ken2
CC=golang-dev
https://golang.org/cl/2471043

R=r, r2
CC=golang-dev
https://golang.org/cl/2494042

R=stephenm
CC=golang-dev
https://golang.org/cl/2471042

R=r, rsc, r2
CC=golang-dev
https://golang.org/cl/2499041

R=rsc, r
CC=golang-dev
https://golang.org/cl/2473041

R=rsc, iant, agl
CC=golang-dev
https://golang.org/cl/2052042

After a fill(), there is nothing to back up.  Make sure UnreadRune
recognizes the situation.

Fixes #1137.
(Stops the crash, but doesn't make UnreadRune usable after a Peek()).

R=rsc
CC=golang-dev
https://golang.org/cl/2498041

The remaining failures include:

* something about bit operations?
	crypto/block
	encoding/binary

* something about file I/O?
	archive/tar
	archive/zip
	debug/dwarf
	debug/elf
	debug/macho
	image/png

* floating point
	cmath
	expvar
	flag
	fmt
	gob
	json
	math
	strconv
	template
	xml

* network (maybe fixed by a pending CL)
	http
	netchan
	rpc
	rpc/jsonrpc
	syslog
	websocket

* line numbers
	log

* haven't bothered / not sure
	exp/datafmt
	exp/eval
	go/printer
	os
	os/signal
	testing/quick

R=ken2
CC=golang-dev
https://golang.org/cl/2496041

R=rsc
CC=golang-dev
https://golang.org/cl/2475042

The Plan 9 tools assume that long is 32 bits.
We converted all instances of long to int32 when
importing the code but missed the print formats.
Because int32 is always int on the compilers we use,
it is never correct to use %lux, %ld, etc.  Convert to %ux, %d, etc.

(It matters because on 64-bit gcc, long is 64 bits,
so we were printing 32-bit quantities with 64-bit formats.)

R=ken2
CC=golang-dev
https://golang.org/cl/2491041

* Maintain Sym* list for text with individual
  prog lists instead of using one huge list and
  overloading p->pcond.
* Comment what each file is for.
* Move some output code from span.c to asm.c.
* Move profiling into prof.c, symbol table into symtab.c.
* Move mkfwd to ld/lib.c.
* Throw away dhog dynamic loading code.
* Throw away Alef become.
* Fix printing of WORD instructions in 5l -a.

Goal here is to be able to handle each piece of text or data
as a separate piece, both to make it easier to load the
occasional .o file and also to make it possible to split the
work across multiple threads.

R=ken2, r, ken3
CC=golang-dev
https://golang.org/cl/2335043

This is entirely adding and removing tabs.
It looks weird but will make the diffs for the
next change easier to read.

R=ken2
CC=golang-dev
https://golang.org/cl/2490041

R=rsc
CC=golang-dev
https://golang.org/cl/2485041

R=rsc
CC=golang-dev
https://golang.org/cl/2472041

R=r, r2
CC=golang-dev
https://golang.org/cl/2469041

Use a bytes.Buffer in log writing instead of string concatenation.
Should reduce the number of allocations significantly.

R=rsc, r2
CC=golang-dev
https://golang.org/cl/2417042

R=adg
CC=golang-dev
https://golang.org/cl/2468041

R=r, r2, rsc, uriel
CC=golang-dev
https://golang.org/cl/2433042

Fixes some race conditions.

R=r
CC=golang-dev
https://golang.org/cl/2456041

6l was skipping emitting the (2 byte) symbol table if there were no imported or exported
symbols. You can't just drop the symbol table entirely - the linker dies if you have
a linkedit section but no table. You can omit the linkedit section or both the linkedit
and the dlyd parts in the right circumstances, but that seems much more risky to me.

R=rsc
CC=golang-dev
https://golang.org/cl/2421042

New logging interface simplifies and generalizes.

1) Loggers now have only one output.
2) log.Stdout, Stderr, Crash and friends are gone.
	Logging is now always to standard error by default.
3) log.Panic* replaces log.Crash*.
4) Exiting and panicking are not part of the logger's state; instead
	the functions Exit* and Panic* simply call Exit or panic after
	printing.
5) There is now one 'standard logger'.  Instead of calling Stderr,
	use Print etc.  There are now triples, by analogy with fmt:
		Print, Println, Printf
	What was log.Stderr is now best represented by log.Println,
	since there are now separate Print and Println functions
	(and methods).
6) New functions SetOutput, SetFlags, and SetPrefix allow global
	editing of the standard logger's properties.   This is new
	functionality. For instance, one can call
		log.SetFlags(log.Lshortfile|log.Ltime|log.Lmicroseconds)
	to get all logging output to show file name, line number, and
	time stamp.

In short, for most purposes
	log.Stderr -> log.Println or log.Print
	log.Stderrf -> log.Printf
	log.Crash -> log.Panicln or log.Panic
	log.Crashf -> log.Panicf
	log.Exit -> log.Exitln or log.Exit
	log.Exitf -> log.Exitf (no change)

This has a slight breakage: since loggers now write only to one
output, existing calls to log.New() need to delete the second argument.
Also, custom loggers with exit or panic properties will need to be
reworked.

All package code updated to new interface.

The test has been reworked somewhat.

The old interface will be removed after the new release.
For now, its elements are marked 'deprecated' in their comments.

Fixes #1184.

R=rsc
CC=golang-dev
https://golang.org/cl/2419042

R=ken2
CC=golang-dev
https://golang.org/cl/2465041

R=adg
CC=golang-dev
https://golang.org/cl/2404043

R=rsc, albert.strasheim
CC=golang-dev
https://golang.org/cl/2356042