Bootstrapping Clang with MemorySanitizer

Hi all,

MemorySanitizer (-fsanitize=memory flag) can now be used to build a
self-hosted Clang. Several tests are still failing (most - due to bugs
in the code), but the third-stage compiler is fully functional and
passes the full test suite.

Instructions are here:
https://code.google.com/p/memory-sanitizer/wiki/BootstrappingClang

Congratulations!