reformat mkstemp like mkdtemp

this is cleaner and makes it easy to impose a limit on the number of
retries later if it seems desirable to do so.

src/temp/mkstemp.c

@@ -12,17 +12,15 @@ char *__mktemp(char *);
 int mkstemp(char *template)
 {
 	int fd;
-retry:
-	if (!__mktemp(template)) return -1;
-	fd = open(template, O_RDWR | O_CREAT | O_EXCL, 0600);
-	if (fd >= 0) return fd;
-	if (errno == EEXIST) {
+	for (;;) {
+		if (!__mktemp(template)) return 0;
+		if ((fd = open(template, O_RDWR | O_CREAT | O_EXCL, 0600))>=0)
+			return fd;
+		if (errno != EEXIST) return -1;
 		/* this is safe because mktemp verified
 		 * that we have a valid template string */
 		strcpy(template+strlen(template)-6, "XXXXXX");
-		goto retry;
 	}
-	return -1;
 }
 
 LFS64(mkstemp);