[PATCH] Introduce SANITIZER_HAS_WEAK_SYMBOL and use it for SymbolizerPrepareForSandboxing.

[Dmitry Vyukov]

  Thanks!
  I would prefer to define SymbolizerPrepareForSandboxing() on all platforms, and then just call it. That's what we do now with other functions.

http://llvm-reviews.chandlerc.com/D877