Set correct object level for statue contents

Yet another NitroHack Global Level Pointer Bug.  This one caused crashes
when trying to use an object's olev field for anything during special
level creation since it was being set to null.

This is meant to go with commit 1187aabd31 (don't refer to u.uz during
level creation).
Only try to move timers/lights if object has them

This is a minor optimisation that prevents repeatedly looping through
the level timers and lights lists for the majority of objects that don't
have either.

This is meant to go with commit 90f16c9c59 (move lights/timers with
objects that change levels).
Update commment in transfer_lights()

This is meant to go with commit 90f16c9c59 (move lights/timers with
objects that change levels).
Clean up timer debugging code
Bump patchlevel to 0.5.5

This release fixes a NitroHack bug with statue contents that interacted
badly with 0.5.4's timer/light source fix causing the game to crash when
entering a level with such statues.