Reorganize test/Modules:

 * Put all input files under Inputs/, move corresponding tests into test/Modules.
 * Rename a modulemap test file to [...].modulemap, and teach lit that such files are tests.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@226875 91177308-0d34-0410-b5e6-96231b3b80d8