training/unicharset_extractor.cpp: Print whether WCTYPE is included

Character properties are autogenerated only if wctype is found on the
system.  However, it is not possible to know if a version of
unicharset_extractor was compiled with this support (especially if it
was installed as a pre-compiled binary).

This commit adds a print to the usage details to output if the binary
was compiled with wctype support.

training/unicharset_extractor.cpp

@@ -105,6 +105,11 @@ int main(int argc, char** argv) {
   // Print usage
   if (argc <= 1) {
     printf("Usage: %s [-D DIRECTORY] FILE...\n", argv[0]);
+#ifdef USING_WCTYPE
+    printf("Character properties using wctype is enabled\n");
+#else
+    printf("WARNING: Character properties using wctype is DISABLED\n");
+#endif
     exit(1);
 
   }