[modules] Check for delegating constructor cycles when building a module and don't write them out to the module file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177000 91177308-0d34-0410-b5e6-96231b3b80d8
[modules] Don't write the UnusedFileScopedDecls vector to the module file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177001 91177308-0d34-0410-b5e6-96231b3b80d8