Summon AI fix

A bug which became much more prominent with introduction of temporal clones (which have high chance to have access to less-than-a-turn talents) and Temporal Fugue in particular (where turns not ticking down AT ALL when AI is far from player becomes a serious concern.)

This commit makes for a more predictable and accurate summon_time behaviour, making it tick down in NPC.actBase if ai is "summoned" and the creature isn't out of timeflow.

IMPORTANT: considerations need to be made for Mucus Oozes (which have 70% global speed) and Bloated Oozes (50%), as it effectively brings their summon time to what's advertised (6-10 turns.) Whether this is desirable needs to be decided.