(1) Collect headers under inner frameworks (frameworks inside other
other frameworks).
(2) Make sure we also collect the right header files inside them.

More info on (2):

Consider a dummy framework module B, with header Frameworks/B/B.h. Now
consider that another framework A, with header Frameworks/A/A.h, has a
layout with a inner framework Frameworks/A/Frameworks/B/B.h, where the
"B/B.h" part is a symlink for Frameworks/B/B.h. Also assume that
Frameworks/A/A.h includes <B/B.h>.

When parsing header Frameworks/A/A.h, framework module lookup is
performed in search for B, and it happens that
"Frameworks/A/Frameworks/B/B.h" path is registered in the module instead
of real "Frameworks/B/B.h". This occurs because
"Frameworks/A/Frameworks/B/B.h" is scanned first by the FileManager,
when looking for inner framework modules under Frameworks/A/Frameworks.
This makes Frameworks/A/Frameworks/B/B.h the default cached named inside
the FileManager for the B.h file UID.

This leads to modules being built without consistent paths to underlying
header files. This is usually not a problem in regular compilation flow,
but it's an issue when running the crash reproducer. The issue is that
clangs collect "Frameworks/A/Frameworks/B/B.h" but not
"Frameworks/B/B.h" into the VFS, leading to err_mmap_umbrella_clash. So
make sure we also collect the original header.

Differential Revision: http://reviews.llvm.org/D20194

rdar://problem/25880368

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@269502 91177308-0d34-0410-b5e6-96231b3b80d8