Parser is gc-aware now.

But for the rest...
Working on Codegen2.

Not a complete rewrite, just adding gc to the compiler itself.
Most of the stl-related code are replaced by gc-aware containers.
Can compile primitive ops now.
FrameDescr done, but gc is not working correctly..

Valgrind barf about using uninitialized values. Might have somthing to do
with the GcHeader (and strict aliasing rules?)
Fixed valgrind errors.

It seems that my code is fine and I just need to add
VALGRIND_DISCARD_TRANSLATIONS in gc code... WTF
Cleanup and prepare for merging back to master.

Next step is to add more prim-ops and special-ops.