- Rework secondary expansion so we only defer it if there's a possibility

it might be needed: for most situations we parse prereqs immediately as
  we used to.  Reduces memory usage.
- Fixes Savannah bug #18622.

default.c

@@ -542,8 +542,9 @@ set_default_suffixes (void)
   else
     {
       char *p = default_suffixes;
-      suffix_file->deps = (struct dep *)
-	parse_file_seq (&p, sizeof (struct dep), '\0', NULL, 0);
+      suffix_file->deps = enter_prereqs(PARSE_FILE_SEQ (&p, struct dep, '\0',
+                                                        NULL, 0),
+                                        NULL);
       define_variable ("SUFFIXES", 8, default_suffixes, o_default, 0);
     }
 }