Expose sector.touching_thinglist and mo.touching_sectorlist to Lua

Unimplemented for the longest time, you can now grab a list of the sectors a mobj is touching.

Also, sector.touching_thinglist is included, which unlike sector.thinglist also tracks mobjs whose hitboxes are inside the sector.

The syntax for both is identical to the other sector iterators:

for sec in mo.touching_sectorlist() do

or

for mo in sectors[0].touching_thinglist() do