[Sema][OpenCL] Improve diagnostics for not viable overloadable function candidates

Summary:
Allowed extension name (that ought to be disabled) printing in the note message.

This diagnostic was proposed here: https://reviews.llvm.org/D51341

Reviewers: Anastasia, yaxunl

Reviewed By: Anastasia

Subscribers: cfe-commits, asavonic, bader

Differential Revision: https://reviews.llvm.org/D52292

llvm-svn: 344246
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index a5a51d5..a8d69ea 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -10242,7 +10242,8 @@
   FunctionDecl *Callee = Cand->Function;
 
   S.Diag(Callee->getLocation(),
-         diag::note_ovl_candidate_disabled_by_extension);
+         diag::note_ovl_candidate_disabled_by_extension)
+    << S.getOpenCLExtensionsFromDeclExtMap(Callee);
 }
 
 /// Generates a 'note' diagnostic for an overload candidate.  We've