[Wish] uv_loop_t time can option use high resolution time on windows

[DZLiao]

Some applications need to use high resolution time because the time is sensitive some applications, like video stream. I known that use high resolution time is affect the performance. So maybe it can be optional on windows platform.

First the uv_loop_t add new flag for identify use high resolution time or not. Second, when uv_run() call uv_update_time() check the flag use uv_hrtime() or GetTickCount().

This is my suggestion and flexible for developers.

void uv_update_time(uv_loop_t* loop) {

  // --- Extend begin
  if (loop->use_hrtime == 1) {
    loop->time = uv_hrtime()/1000000;
    return;
  }
  // --- Extend end

  DWORD ticks = GetTickCount();

  /* The assumption is made that LARGE_INTEGER.QuadPart has the same type */
  /* loop->time, which happens to be. Is there any way to assert this? */
  LARGE_INTEGER* time = (LARGE_INTEGER*) &loop->time;

  /* If the timer has wrapped, add 1 to it's high-order dword. */
  /* uv_poll must make sure that the timer can never overflow more than */
  /* once between two subsequent uv_update_time calls. */
  if (ticks < time->LowPart) {
    time->HighPart += 1;
  }
  time->LowPart = ticks;
}

[saghul]

You may want to check this out: #1165

[saghul]

#1165 landed, closing.