Remove all trailing blanks; turn on the rule to detect them.

* Makefile.cfg (local-checks-to-skip): Remove sc_trailing_blank.
* .x-sc_trailing_blank: New file, to exempt the few binary files.

tests/xml2sexprtest.c

@@ -256,7 +256,7 @@ main(int argc, char **argv)
         fprintf(stderr, "missing enviroment variable abs_top_srcdir\n");
 	exit(EXIT_FAILURE);
     }
-        
+
 
     if (argc > 1) {
 	fprintf(stderr, "Usage: %s\n", progname);