Added testcase for some part of PR #1833.

test/val/pr1833.c

@@ -0,0 +1,13 @@
+/* Test for PR #1833 fixes */
+
+#define char 1
+
+#if char && !int && L'A' - L'B' == 'A' - 'B' && L'A' == 'A'
+#else
+#error
+#endif
+
+int main(void)
+{
+    return 0;
+}