Rip out the last remaining implicit use of OverloadedFunctionDecl in Sema:
LookupResult::getAsSingleDecl() is no more.  Shift Sema::LookupSingleName to
return null on overloaded results.

llvm-svn: 90309
diff --git a/clang/lib/Sema/Sema.h b/clang/lib/Sema/Sema.h
index 8503887..98880e9 100644
--- a/clang/lib/Sema/Sema.h
+++ b/clang/lib/Sema/Sema.h
@@ -1160,7 +1160,7 @@
   }
 
   /// \brief Look up a name, looking for a single declaration.  Return
-  /// null if no unambiguous results were found.
+  /// null if the results were absent, ambiguous, or overloaded.
   ///
   /// It is preferable to use the elaborated form and explicitly handle
   /// ambiguity and overloaded.