Consider module depedencies when checking a preamble in libclang

Consider module depedencies when checking a preamble in libclang

Add module dependencies (header files, module map files) to the list of
files to check when deciding whether to rebuild a preamble. That fixes
using preambles with module imports so long as they are in
non-overridden files.

My intent is to use to unify the existing dependency collectors to the
new “DependencyCollectory” interface from this commit, starting with the
DependencyFileGenerator.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@212060 91177308-0d34-0410-b5e6-96231b3b80d8