clang-format: Improve stream-formatting.

Before:
  CHECK(controller->WriteProto(FLAGS_row_key, FLAGS_proto)) << "\""
                                                            << FLAGS_proto
                                                            << "\"";

After:
  SemaRef.Diag(Loc, diag::note_for_range_begin_end)
      << BEF << IsTemplate << Description << E->getType();

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188175 91177308-0d34-0410-b5e6-96231b3b80d8
SourceManager intialization tweaks.

- Open files before calling stat on them.
- Go through FileManager for getting the buffer of named pipes. It has the
  necessary plumbing to deal with "volatile" files.
- Print the cause when stdin reading fails. The only case I can imagine where
  this happens is when stdin is wired to a device file, so no test case.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188178 91177308-0d34-0410-b5e6-96231b3b80d8