Removes some old code that allowed a module to be loaded from a pcm file
even if the module.map could not be found. Also update a number of
tests that relied on the old behavior.
llvm-svn: 199852
turns out that it's actually needed for C++ modules support. Since simplifying
it didn't cause any test failures, I'll add a test for it.
llvm-svn: 154582
Ben Langmuir