Add a CastKind enum to CastExpr. Right now it's not used for much but it will be :)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@77650 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 2ec318c..ff3b4ef 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -2335,6 +2335,7 @@
   DeclRefExpr ConversionRef(Conversion, Conversion->getType(), 
                             SourceLocation());
   ImplicitCastExpr ConversionFn(Context.getPointerType(Conversion->getType()),
+                                CastExpr::CK_Unknown,
                                 &ConversionRef, false);
   
   // Note that it is safe to allocate CallExpr on the stack here because