[Preprocessor] Add a note with framework location for "file not found" error.

When a framework with the same name is available at multiple framework
search paths, we use the first matching location. If a framework at this
location doesn't have all the headers, it can be confusing for
developers because they see only an error `'Foo/Foo.h' file not found`,
can find the complete framework with required header, and don't know the
incomplete framework was used instead.

Add a note explaining a framework without required header was found.
Also mention framework directory path to make it easier to find the
incomplete framework.

rdar://problem/39246514

Reviewers: arphaman, erik.pilkington, jkorous

Reviewed By: jkorous

Subscribers: jkorous, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D56561

llvm-svn: 353231