passwd: rework:

* do not make backup copy by copying (just retain old file)
* correctly fall back to /etc/passwd if user is not in shadow
* fix bug with overlong passwd entries
* be permissive on some kinds of failures
* reduce stack usage
* code size: -500 bytes

editors/patch.c

@@ -117,12 +117,14 @@ int patch_main(int argc, char **argv)
 			free(patch_line);
 			patch_line = xmalloc_fgets(patch_file);
 		}
+		/* FIXME: patch_line NULL check?? */
 
 		/* Extract the filename used before the patch was generated */
 		original_filename = extract_filename(patch_line, patch_level);
 		free(patch_line);
 
 		patch_line = xmalloc_fgets(patch_file);
+		/* FIXME: NULL check?? */
 		if (strncmp(patch_line, "+++ ", 4) != 0) {
 			ret = 2;
 			bb_error_msg("invalid patch");