See through UsingDecls in more places.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74269 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index 93bee84..5815d82 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -97,6 +97,9 @@
 }
 
 bool Decl::isFunctionOrFunctionTemplate() const {
+  if (const UsingDecl *UD = dyn_cast<UsingDecl>(this))
+    return UD->getTargetDecl()->isFunctionOrFunctionTemplate();
+    
   return isa<FunctionDecl>(this) || isa<FunctionTemplateDecl>(this);
 }