AST/ExprConstant.cpp: Silence a warning on ms cl.exe. "bool" does not prefer to be compared to integer.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149059 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 6a292c3..63d01de 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -503,7 +503,7 @@
 
   for (FunctionDecl::param_const_iterator I = Frame->Callee->param_begin(),
        E = Frame->Callee->param_end(); I != E; ++I, ++ArgIndex) {
-    if (ArgIndex > IsMemberCall)
+    if (ArgIndex > (unsigned)IsMemberCall)
       Out << ", ";
 
     const ParmVarDecl *Param = *I;