util/clock.c: Apply clock skew

SEGA games are unplayable between 03:00 and 07:00 local time due
to a network maintenance period that is hard-coded into the games
themselves (no, guest play is not available).

Deal with this by slowing down time to avoid 02:00 (the time when
a warning appears and new credits eventually start being rejected),
then jump forward to sync up with real time when 07:00 hits.

util/clock.h

@@ -1,3 +1,4 @@
 #pragma once
 
-void clock_hook_init(void);
+void clock_set_hook_init(void);
+void clock_skew_hook_init(void);