Add missing <cctype> include, from Joerg Sonnenberger

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123668 91177308-0d34-0410-b5e6-96231b3b80d8

tools/driver/driver.cpp

@@ -35,6 +35,7 @@
 #include "llvm/Support/Program.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/system_error.h"
+#include <cctype>
 using namespace clang;
 using namespace clang::driver;