optimize regex handling

some fixes and cleanups

Another 2.7.9 compatibility fix

- copy CPython's implementation (that uses C slots)
- implement the C slots for str and list
- avoid doing a division for non-step slices

It was unused

Particularly for string slicing, where we would
always memset the string data to zero, and then
immediately memcpy it.

- put it into a header file (and start including it)
- move the grow-the-array part into a separate function
  to encourage the fast-path to get inlined.

This division is expensive; the divisor is always sizeof(char) or sizeof(Py_UNICODE),
and it seems to be faster to do a branch and then possibly a shift.

int(str) and int(float) don't always return ints (cant return longs, doh).
If we call int() on a subclass of int, we should call its __int__ method in
case the subclass overrode it.

And some other small cleanups

This only does the lexing portion of the process.

Further cut that down into a re.split ubench

Some refactors in GC code + class-freed-before-instance bug fix.

Add sre_compile_test.expected

In some rare instances, class objects can be freed before the last
instance of that class, causing a problem in the sweep phase where
we look at the class of the object being freed.

So we keep unreachable classes around for an extra collection to be
safe.

This reverts commit e0bd51eb.

Ie, manually specify the reference output for sre_compile_test.py instead
of running CPython to generate it.  CPython changed the behavior (and interface)
of _optimize_charset at some point between 2.7.7 (where we copied from) and
2.7.9.

We should probably copy their new implementation (seems to have a few more
optimizations), but for now this should fix #707.

jemalloc

some misc microoptimizations

Yes they exist, for example "try getting this attribute
and if it exists call it, otherwise do something else".
Probably not a huge perf improvement since the
exception-throwing will probably dominate.

Use the same "only do this for immortal strings" trick to get
around gc issues.

Only do this for calls with immortally-interned strings so that
we can side-step the track-gc-references-in-ics issue for now.

type speculation support

I have a whole bunch of mechanical changes to allow speculation, but
I think our pre-existing speculation rules end up hurting the macrobenchmarks.
I'd like to get those in and then separately work on making in beneficial.

It'll break once we add frame introspection info to it, but
for now it just needed some massaging.

Currently it gets somewhat hidden by the object-caching behavior.
Add an API for fetching it out, and use it to make the "prettified"
IR (which you see on -vv or higher) include the slowpath addresses.

Using NULL for undefined values is confusing since maybe
something actually returned that.  So try using -1.

Somewhat ad-hoc at the moment; only added for a few types
of operations.

Add a couple tests to the travis-ci configuration

correct output filenames for the new .so's