libbb: introduce and use xrename and rename_or_warn.

editors/patch.c

@@ -150,10 +150,7 @@ int patch_main(int argc, char **argv)
 			backup_filename = xmalloc(strlen(new_filename) + 6);
 			strcpy(backup_filename, new_filename);
 			strcat(backup_filename, ".orig");
-			if (rename(new_filename, backup_filename) == -1) {
-				bb_perror_msg_and_die("cannot create file %s",
-						backup_filename);
-			}
+			xrename(new_filename, backup_filename);
 			dst_stream = xfopen(new_filename, "w");
 		}
 

editors/sed.c

@@ -1340,8 +1340,7 @@ int sed_main(int argc, char **argv)
 
 			G.nonstdout = stdout;
 			/* unlink(argv[i]); */
-			// FIXME: error check / message?
-			rename(G.outname, argv[i]);
+			xrename(G.outname, argv[i]);
 			free(G.outname);
 			G.outname = NULL;
 		}