Use wchar.h to get wchar_t, not ctype.h.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78703 91177308-0d34-0410-b5e6-96231b3b80d8

test/FrontendC/wchar-const.c

@@ -1,6 +1,6 @@
 // RUN: %llvmgcc -S %s -o - | grep {constant \\\[18 x} | grep { 84, }
 // This should pass for any endianness combination of host and target.
-#include <ctype.h>
+#include <wchar.h>
 extern void foo(const wchar_t* p);
 int main (int argc, const char * argv[])
 {