Add simple_copying.
Junk.
Add a shadow stack.
Random tweaks.
Start work on Parallel collector.

--HG--
rename : simple_copying/Makefile => parallel_copying/Makefile
rename : simple_copying/alloc.c => parallel_copying/alloc.c
rename : simple_copying/alloc.h => parallel_copying/alloc.h
rename : simple_copying/shadowstack.c => parallel_copying/shadowstack.c
rename : simple_copying/shadowstack.h => parallel_copying/shadowstack.h
rename : simple_copying/test_app.c => parallel_copying/test_app.c
Work on the initial form of the parallel collector.
Add hgignore
CLoser. It actually runs but not really correctly yet.
Work on thread finalization.
Merge changes from GitHub