[Preprocessor] Hide include typo correction behind SpellChecking.

Summary:
Similar to Sema typo correction, the Preprocessor typo correction should
also be hidden behind the SpellChecking flag.

Reviewers: sammccall

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D52778

llvm-svn: 343591

clang/lib/Lex/PPDirectives.cpp

@@ -1888,7 +1888,7 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
       // Check for likely typos due to leading or trailing non-isAlphanumeric
       // characters
       StringRef OriginalFilename = Filename;
-      if (!File) {
+      if (LangOpts.SpellChecking && !File) {
         // A heuristic to correct a typo file name by removing leading and
         // trailing non-isAlphanumeric characters.
         auto CorrectTypoFilename = [](llvm::StringRef Filename) {