Include llvm::Optional in clang/Basic/LLVM.h

Post-commit CR feedback from Jordan Rose regarding r175594.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175679 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index f3a290c..e0585df 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -2080,7 +2080,7 @@
   CharSourceRange LMRange = getSpecifierRange(LM.getStart(), LM.getLength());
 
   // See if we know how to fix this length modifier.
-  llvm::Optional<LengthModifier> FixedLM = FS.getCorrectedLengthModifier();
+  Optional<LengthModifier> FixedLM = FS.getCorrectedLengthModifier();
   if (FixedLM) {
     EmitFormatDiagnostic(S.PDiag(DiagID) << LM.toString() << CS.toString(),
                          getLocationOfByte(LM.getStart()),
@@ -2113,7 +2113,7 @@
   CharSourceRange LMRange = getSpecifierRange(LM.getStart(), LM.getLength());
 
   // See if we know how to fix this length modifier.
-  llvm::Optional<LengthModifier> FixedLM = FS.getCorrectedLengthModifier();
+  Optional<LengthModifier> FixedLM = FS.getCorrectedLengthModifier();
   if (FixedLM) {
     EmitFormatDiagnostic(S.PDiag(diag::warn_format_non_standard)
                            << LM.toString() << 0,
@@ -2140,7 +2140,7 @@
   using namespace analyze_format_string;
 
   // See if we know how to fix this conversion specifier.
-  llvm::Optional<ConversionSpecifier> FixedCS = CS.getStandardSpecifier();
+  Optional<ConversionSpecifier> FixedCS = CS.getStandardSpecifier();
   if (FixedCS) {
     EmitFormatDiagnostic(S.PDiag(diag::warn_format_non_standard)
                           << CS.toString() << /*conversion specifier*/1,