struct definitions that end with semicolons

If we use clang to build bpftrace instead of GCC, it will complain about
trying to use the `-std-c++14` flag to comile headers.c. If we force
cmake to skip this flag on `.c` files, clang is not able to link
libresources.a correctly.

This patch changes the resources workflow to generate a .cpp file
instead, and to have a `src/headers.h` with all headers we currently
use. With this approach we get a safer linkage because the same
definition for the header strings is being used in clang_parser.cpp and
in headers.cpp.

Fixes: https://github.com/iovisor/bpftrace/issues/350

bpftrace -l tweaks for consistency

Fix wrong package name in build instructions

This corresponds to the change in the install instructions for Ubuntu
outlined in #335.

Make bpftrace -l list sofware and hardware types (#44)

tracepoint shortcut t breaks args

hist: split negative, zero, and one into separate buckets

Add --version

- Also refactored code in attached_probe.cpp and
ast/semantic_analyzer.cpp to use the sw/hw lists instead of the
hardcoded probe names.

lhist: interval notation tweak

runqlat.bt: remove if semicolon

if semicolon

Link against system bcc

Previously, bpftrace was clone bcc from github at build time, building
a version of bcc, then linking against the built bcc. This is a no-go
for many packaging systems including Fedora, openSUSE, and the internal
Facebook one.

This patch requires bcc and bcc development headers be installed to
build bpftrace and removes the build time downloading behavior.
Also simplifies some of the header search logic.

Test plan:
```
$ ./build/tests/bpftrace_test
...
$ sudo make -C build runtime-tests
...

$ cat ~/scratch/bpftrace/path.bt

kprobe:vfs_open
{
    printf("open path: %s\n", str(((path *)arg0)->dentry->d_name.name));
}

$ sudo ./build/src/bpftrace ~/scratch/bpftrace/path.bt
[sudo] password for dlxu:
Attaching 1 probe...
open path: stat
open path: user-745673103.journal
open path: user-1001.journal
open path: user-745673103.journal
open path: user-1001.journal
open path: user-745673103.journal
open path: user-1001.journal
open path: iio:device0
open path: stat
...

`*-inl.h` files, or inline headers, are an implementation detail. Users
of an interface that is backed by an inline header should not concern
themselves with the details of implementation.

This patch normalizes the interface.

Avoid crashing if mistakenly just '-d' or '-v' is used

Currently, if by mistake just '-v' or '-d' is used without any
additional parameter (no filename nor -e 'program') bpftrace crashes:

./src/bpftrace -v
terminate called after throwing an instance of 'std::logic_error'
what():  basic_string::_M_construct null not valid
Aborted (core dumped)

This commit fix this problem.

Return cleanly after printing help

Test plan:
```
 $ ./build/src/bpftrace -h &> /dev/null && echo $?
 0
```

This allows operators to use other tools, like bpftool, to
introspect a running program.
Signed-off-by: David Calavera <david.calavera@gmail.com>

Fix use-after-free in BPFtrace::get_arg_values

Docs