[libclang] If displayDiagnostics is set (when calling clang_createIndex), make sure to
output the errors that occurred even if we did not get an AST (e.g. because the
PCH failed to load).

Also honor displayDiagnostics in clang_indexSourceFile().

rdar://11203489

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154472 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed