Fix MSVC build.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94809 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index f020681..af6dc7c 100644
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -20,6 +20,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/ADT/STLExtras.h"
+#include <cctype>
 #include <sys/stat.h>
 #include <sys/types.h>