patch 7.4.1552

Problem:    ":colorscheme" does not use 'packpath'.
Solution:   Also use in "start" and "opt" directories in 'packpath'.

src/option.c

@@ -7290,7 +7290,7 @@ did_set_string_option(
 		if (vim_strchr((char_u *)"_.,", *p) != NULL)
 		    break;
 	    vim_snprintf((char *)fname, 200, "spell/%.*s.vim", (int)(p - q), q);
-	    source_runtime(fname, TRUE);
+	    source_runtime(fname, DIP_ALL);
 	}
 #endif
     }