[PowerPC] Fix memory corruption in AsmParser

As pointed out by Evgeniy Stepanov, assigning a std::string temporary
to a StringRef is not a good idea.  Rework MatchRegisterName to avoid
using the .lower routine.
[asan] Common flags in ASan.

Some flags that are common to ASan/MSan/TSan/LSan have been moved to
sanitizer_common.
[msan] Common flags in MSan.
Free the exception object. Should fix the vg bots.
Added Mozilla style, cleaned get*Style methods.

Summary: Patch based on a patch by Ehsan Akhgari.

Reviewers: djasper

Reviewed By: djasper

CC: cfe-commits, klimek

Differential Revision: http://llvm-reviews.chandlerc.com/D750
Add llvm_unreachable at end of fully covered switch

To pacify GCC warning about control reaching end of non-void function.
Remove forward slashes from check; should unbreak Windows buildbots.