unbreak buildbot on Windows.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188018 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/ARCMigrate/ObjCMT.cpp b/lib/ARCMigrate/ObjCMT.cpp
index 14d5cf6..46d538e 100644
--- a/lib/ARCMigrate/ObjCMT.cpp
+++ b/lib/ARCMigrate/ObjCMT.cpp
@@ -277,7 +277,7 @@
     PropertyNameStringRef = PropertyNameStringRef.drop_front(2);
     PropertyNameString = PropertyNameStringRef;
     std::string NewPropertyNameString = PropertyNameString;
-    NewPropertyNameString[0] = std::tolower(NewPropertyNameString[0]);
+    NewPropertyNameString[0] = toLowercase(NewPropertyNameString[0]);
     PropertyString += NewPropertyNameString;
   }
   else