Issue a good diagnostics when attempt to select
a type convesion function results in ambiguity.

llvm-svn: 81812
diff --git a/clang/lib/Sema/Sema.h b/clang/lib/Sema/Sema.h
index 1811f29..d2034ce 100644
--- a/clang/lib/Sema/Sema.h
+++ b/clang/lib/Sema/Sema.h
@@ -772,6 +772,7 @@
   bool IsQualificationConversion(QualType FromType, QualType ToType);
   bool IsUserDefinedConversion(Expr *From, QualType ToType,
                                UserDefinedConversionSequence& User,
+                               OverloadCandidateSet& Conversions,
                                bool AllowConversionFunctions,
                                bool AllowExplicit, bool ForceRValue);