Always exit TryRunTics loop early if deferring gamestate change

Calls to F_ContinueCredits and D_StartTitle, even if deferred,
change the current gamestate. However, the tic loop in TryRunTics
may still have a couple tics to execute to catch up to current
time, and as a consequence G_Ticker may execute game logic while
the current state is not GS_LEVEL or equivalent. As a result, it is
highly likely for the game to crash.

This adds deferred credits start to the tic loop, and exits that
loop if either title or credits are supposed to start after the
current iteration, fixing this crash scenario.

Fixes KartKrew/Kart#1185