Add a IsInstrumentationRuntimePresent SB API

Reviewed at http://reviews.llvm.org/D5738

This adds an SB API into SBProcess:
  bool SBProcess::IsInstrumentationRuntimePresent(InstrumentationRuntimeType type);
which simply tells whether a particular InstrumentationRuntime (read "ASan") plugin is present and active.

llvm-svn: 219560