Add missing standard includes. Patch by Joerg Sonnenberger!

llvm-svn: 122194
diff --git a/clang/lib/Lex/HeaderMap.cpp b/clang/lib/Lex/HeaderMap.cpp
index be3f701..e424f91 100644
--- a/clang/lib/Lex/HeaderMap.cpp
+++ b/clang/lib/Lex/HeaderMap.cpp
@@ -18,6 +18,7 @@
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include <cctype>
 #include <cstdio>
 using namespace clang;