Roughly double Hellfire damage

The unrand arbalest, that is. From 2d5 to 3d8.

It was generally considered quite weak, and testing confirmed
that. For the cost of mulching all your ammo & making a lot of
noise, an unrand should give significantly more benefit than 2d5!
only weight randlich secondary spells

we were getting an unreasonably high rate of invisibility, because it
was the only hexes buff spell. similar issues with the conj primary
spells for ancient liches, since they would pair up more often
don't give virulence without other poison spells
Remove the shop hack.

You will be neither missed nor forgotten!

Tested save compat on old levels with one shop, with multiple shops,
and with new shops.
Refactor place_spec_shop a bit.
Don't call ball lightning creatures, either.
Replace a boolean field with a flag.
s/RETURN_FROM_/EXIT_/g
Arguably move recite text to data.

Unfortunately, there's still no simple way to add a new verse because
of the way that the hashing works; along the same lines, moving the
text to the database is non-trivial.
Merge https://github.com/crawl-ref/crawl-ref