Kill -faddress-sanitizer, -fthread-sanitizer and -fcatch-undefined-behavior flags.

These flags are deprecated since at least Clang 3.3. Users should instead
use -fsanitize= with appropriate values.
[ASan] Do not instrument globals from the llvm.metadata section.
Fixes https://code.google.com/p/address-sanitizer/issues/detail?id=279.