This patch exposes to Clang users three more sanitizers are experimental features...

This patch exposes to Clang users three more sanitizers are experimental features of ASan:
1) init-order sanitizer: initialization-order checker.
Status: usable, but may produce false positives w/o proper blacklisting.
2) use-after-return sanitizer
Status: implemented, but heavily understed.
Should be optional, as it significanlty slows program down.
3) use-after-scope sanitizer
Status: in progress.

llvm-svn: 168950