eliminate mk*temp dependency on snprintf

this helps some tiny programs be even more tiny, and barly increases
code size even if both are used.

src/temp/mktemp.c

@@ -11,9 +11,9 @@
 char *__mktemp(char *template)
 {
 	struct timespec ts;
-	size_t l = strlen(template);
+	size_t i, l = strlen(template);
 	int retries = 10000;
-	unsigned long r;
+	unsigned long r, t;
 
 	if (l < 6 || strcmp(template+l-6, "XXXXXX")) {
 		errno = EINVAL;
@@ -23,7 +23,8 @@ char *__mktemp(char *template)
 	clock_gettime(CLOCK_REALTIME, &ts);
 	r = ts.tv_nsec + (uintptr_t)&ts / 16 + (uintptr_t)template;
 	while (retries--) {
-		snprintf(template+l-6, 7, "%06lX", r & 0xffffff);
+		for (t=r, i=1; i<=6; i++, t>>=4)
+			template[l-i] = 'A'+(t&15);
 		if (access(template, F_OK) < 0) return template;
 		r = r * 1103515245 + 12345;
 	}