[tsan] Implement a 'ignore_noninstrumented_modules' flag to better suppress false positive races

On Darwin, we currently use 'ignore_interceptors_accesses', which is a heavy-weight solution that simply turns of race detection in all interceptors. This was done to suppress false positives coming from system libraries (non-instrumented code), but it also silences a lot of real races. This patch implements an alternative approach that should allow us to enable interceptors and report races coming from them, but only if they are called directly from instrumented code.

The patch matches the caller PC in each interceptors. For non-instrumented code, we call ThreadIgnoreBegin.

The assumption here is that the number of instrumented modules is low. Most likely there's only one (the instrumented main executable) and all the other modules are system libraries (non-instrumented).

Differential Revision: https://reviews.llvm.org/D28264

llvm-svn: 291631