[PATCH] [msan] Rewrite strto* interceptors and add a few more.

[Evgeniy Stepanov]

  The fact that there is an strtol interceptor in asan means there is _something_ to achieve, right? :)
  Common interceptors would do READ on the input string, and let us catch asan bugs and tsan data races on that memory.
  ASan interceptor has interesting look ahead logic that should also be merged to the common interceptor.

  OK to do it in a separate commit later.
  LGTM.

http://llvm-reviews.chandlerc.com/D2629

BRANCH
  msan/strto

ARCANIST PROJECT
  compiler-rt