Previously things were hardcoded to only allow a single entry point to
the interpreter (since that is how the unwinder determines if the frame
is an interpreter frame).

Instead of having astInterpretFunction be the interpreter frame, make
execute() the frame.  Have to make it a static class function so we can
take its address.

Can still switch back to the default regalloc using the -b flag,
but it looks like the basic register allocator cuts the LLVM JIT
time significantly, and improves every one of our benchmarks.

With the recent package import support, we broke importing optparse.
This is because we now can import "encodings" (a package), which imports
codecs, which raises a SystemError when trying to import _codecs which
we don't support yet.

This was getting ignored before since optparse wrapped this process
(which happens via "import gettext") in a try-except and catches the
ImportError.

Add missing FloorDivInt test

Cmake fixes for #231 and #232

load package/__init__.py if it exists, and set its __path__

my old one was missing a std::move and did not accept lvalues.

Controlled by the '-b' command-line flag.  That used to
be for "benchmark" mode but it looks like benchmark mode
has been broken for a while, so remove that.

also, add a test that includes importing both a module with __init__.py and a submodule.

initial cmake support

ie due to reoptimizing the function and then calling into the compiled code.
We could handle this specific case by not treating these as "real" frames
that need to be introspected, but we have these kinds of situations in other
places (reopt from compiled code, osr from either kind) so I'd rather
find a more general improvement.

Before it was recompiling the OSR-entry function every
time it would take an osr exit.

New AST interpreter

- Move internal definitions from header to source file
- Fix root_stack_set bug carried over from llvm_interpreter
- Cut off access to the old llvm interpreter
- Slightly tune the tiering thresholds
 - They seem too high but our LLVM compilation is overly expensive right now
 - Our AST interpreter is also somewhat slow due to its string handling

for consistency

-the Makefile has been moved up from src/Makefile to the top level
-all pyston binaries and unittests (gc, analysis) are also placed in the
top directory

Once we get the AST interpreter in, we can add resume-from-any-point
functionality, which means that we can get rid of the current OSR system.
Maybe we should have done that first, but I thought it would be easy
to get the OSR stuff working.