clang-modernize: Apply replacements using clang-apply-replacements

Summary:
The clang-apply-replacements process is now invoked to apply
replacements between applying transforms. This resulted in a massive
simplification of the tool:
- FileOverrides class no longer needed.
- Change tracking and code formatting no longer needed.
- No more dependency on libclangApplyReplacements.
- Final syntax check is easier to do directly now than with a separate
  header/source pair.

Replacement handling stuff abstracted into a new header/source pair to
de-clutter ClangModernize.cpp somewhat.

Tests updated.

Differential Revision: http://llvm-reviews.chandlerc.com/D1836

llvm-svn: 192032
diff --git a/clang-tools-extra/clang-apply-replacements/tool/ClangApplyReplacementsMain.cpp b/clang-tools-extra/clang-apply-replacements/tool/ClangApplyReplacementsMain.cpp
index bcd6d30..c192718 100644
--- a/clang-tools-extra/clang-apply-replacements/tool/ClangApplyReplacementsMain.cpp
+++ b/clang-tools-extra/clang-apply-replacements/tool/ClangApplyReplacementsMain.cpp
@@ -228,7 +228,7 @@
   if (ErrorCode) {
     errs() << "Trouble iterating over directory '" << Directory
            << "': " << ErrorCode.message() << "\n";
-    return false;
+    return 1;
   }
 
   // Remove the TUReplacementFiles (triggered by "remove-change-desc-files"