Don't use CLOCKS_PER_SEC in w32 timers.

Don't use CLOCKS_PER_SEC in w32 timers.

 src/w32proc.c (TIMER_TICKS_PER_SEC): New macro.
 (timer_loop, getitimer, setitimer): Use it instead of
 CLOCKS_PER_SEC, which is no longer pertinent, since we don't use
 'clock'.
 (w32_get_timer_time): Use 10*TIMER_TICKS_PER_SEC instead of a
 literal 10000.