<rdar://problem/15640353>

Add an hook for the test suite into the OSX-only CrashReporter "App-specific info"

This allows the test suite to set the crash info to the name and file location of every test as the test gets executed
If the test suite crashes, the crash log will then report which test is the culprit, even when not using verbose mode

This only works on OSX, and defaults to not doing anything on other platforms, but OS/platform-specific invocations
can be devised by each individual platform

llvm-svn: 197095