Lua mapthing len

Merged Monster Iestyn requested to merge lua-mapthing-len into next

This branch adds the ability to find out the # of a particular mapthing_t in a map with Lua, by using # behind any mapthing_t variable. E.g.: #mobj.spawnpoint or #mthing.

Fancy this being missing from SRB2, just when I was going to use it to help debug the bad demo issue. 🤣

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