remove duplicated epoch handling, test it

src/util.c

@@ -9,6 +9,22 @@ void mg_bzero(volatile unsigned char *buf, size_t len) {
   }
 }
 
+uint64_t mg_timegm(unsigned int year, unsigned int month, unsigned int day,
+                   unsigned int hour, unsigned int min, unsigned int sec) {
+  static const uint16_t dm[12] = {0,   31,  59,  90,  120, 151,
+                                  181, 212, 243, 273, 304, 334};
+  const uint64_t day_secs = 86400;
+  const uint64_t year_secs = 31536000;
+  unsigned int y, ly;
+  if (year < 1970) return 0;
+  y = year - 1900;
+  ly = month > 2 ? y + 1 : y;
+  return (uint64_t) sec + 60 * min + 3600 * hour +
+         day_secs * (dm[month - 1] + day - 1) + year_secs * (y - 70) +
+         day_secs * ((ly - 69) / 4) - day_secs * ((ly - 1) / 100) +
+         day_secs * ((ly + 299) / 400);
+}
+
 #if MG_ENABLE_CUSTOM_RANDOM
 #else
 bool mg_random(void *buf, size_t len) {