Using mg_snprintf() everywhere

src/log.c

@@ -50,11 +50,11 @@ bool mg_log_prefix(int level, const char *file, int line, const char *fname) {
 void mg_log(const char *fmt, ...) {
   char mem[256], *buf = mem;
   va_list ap;
-  int len = 0;
+  size_t len = 0;
   va_start(ap, fmt);
   len = mg_vasprintf(&buf, sizeof(mem), fmt, ap);
   va_end(ap);
-  s_fn(buf, len > 0 ? (size_t) len : 0, s_fn_param);
+  s_fn(buf, len > 0 ? len : 0, s_fn_param);
   s_fn("\n", 1, s_fn_param);
   if (buf != mem) free(buf);
 }