Fix MSVC warning: <unsafe use of type 'bool' in operation>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@132058 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/TypePrinter.cpp b/lib/AST/TypePrinter.cpp
index aad97fb..4519606 100644
--- a/lib/AST/TypePrinter.cpp
+++ b/lib/AST/TypePrinter.cpp
@@ -978,7 +978,7 @@
     SpecString += '<';
   
   for (unsigned Arg = 0; Arg < NumArgs; ++Arg) {
-    if (SpecString.size() > !SkipBrackets)
+    if (SpecString.size() > unsigned(!SkipBrackets))
       SpecString += ", ";
     
     // Print the argument into a string.