[MSVC Compat] Fix typo correction for inclusion directives.

[vsapsai]

Summary

In MSVC compatibility mode we were checking not the typo corrected
filename but the original filename.

[christylee]

Thanks for catching that!

[vsapsai]

Thanks for the review.

cfe/trunk/lib/Lex/PPDirectives.cpp

if (!SuppressIncludeNotFoundError) {
         auto CorrectTypoFilename = [](llvm::StringRef Filename) {
           Filename = Filename.drop_until(isAlphanumeric);
           while (!Filename.empty() && !isAlphanumeric(Filename.back())) {
             Filename = Filename.drop_back();
           }
           return Filename;
         };
         StringRef TypoCorrectionName = CorrectTypoFilename(Filename);
+        SmallString<128> NormalizedTypoCorrectionPath;
+        if (LangOpts.MSVCCompat) {
+          NormalizedTypoCorrectionPath = TypoCorrectionName.str();
+#ifndef _WIN32
+          llvm::sys::path::native(NormalizedTypoCorrectionPath);
+#endif
+        }
         File = LookupFile(
             FilenameLoc,
-            LangOpts.MSVCCompat ? NormalizedPath.c_str() : TypoCorrectionName,
+            LangOpts.MSVCCompat ? NormalizedTypoCorrectionPath.c_str()
+                                : TypoCorrectionName,
             isAngled, LookupFrom, LookupFromFile, CurDir,
             Callbacks ? &SearchPath : nullptr,
             Callbacks ? &RelativePath : nullptr, &SuggestedModule, &IsMapped);
         if (File) {
           SourceRange Range(FilenameTok.getLocation(), CharEnd);
           auto Hint = isAngled
                           ? FixItHint::CreateReplacement(
                                 Range, "<" + TypoCorrectionName.str() + ">")

cfe/trunk/test/Preprocessor/include-likely-typo.c

 // RUN: %clang_cc1 %s -verify
+// RUN: %clang_cc1 -fms-compatibility %s -verify
 
 #include "<empty_file_to_include.h>" // expected-error {{'<empty_file_to_include.h>' file not found, did you mean 'empty_file_to_include.h'?}}