Enable -Wmismatched-tags
These scripts have moved to the pyston_perf repo
Try to not repeatedly scan through the 'free' bitfield

Seems to help by a couple percent.
Can optimize the initial branch away since we know we'll always execute the loop at least once
allow pyston to run from a directory other than pyston

-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
add cmake as an alternate build system
cmake disable debug info for llvm unless ENABLE_LLVM_DEBUG is ON