Fix build on windows.

Should clang have a config.h or should we use the config.h of llvm or using the preprocessor is OK?  I did a quick fix here, but having a guideline on how to handle non portable function would be great (or ask ted to stop breaking the windows build :)).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@65233 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CFRefCount.cpp b/lib/Analysis/CFRefCount.cpp
index 4d4bd05..a602de2 100644
--- a/lib/Analysis/CFRefCount.cpp
+++ b/lib/Analysis/CFRefCount.cpp
@@ -35,6 +35,10 @@
 
 using namespace clang;
 
+#ifdef _MSC_VER
+#  define strncasecmp _strnicmp
+#endif // #ifdef _MSC_VER
+
 //===----------------------------------------------------------------------===//
 // Utility functions.
 //===----------------------------------------------------------------------===//