Options tile_weapon_offsets and tile_shield_offsets

These allow setting custom weapon and shield tile x,y offsets for use
with tile_player_tile. If only one offset pair is set, the other will
be taken for the hard-coded entries in mcache if they are available,
so the player doesn't have to figure out e.g. weapon offsets when they
only want to adjust the shield.
Fix missing space in br.end and zig milestones (rchandra).
Don't generate buggy buggy jewellery.
Fix ring ID
Arbalest tiles (and shadow fixes)
Don't allow chimera zombies etc.
Ensure random zombies get compatible bases (#6070, #8275, #8457)

Besides spider skeletons from 'place:Foo skeleton', this also avoids
picking M_NO_GEN_DERIVED and non-natural base types.
Remove a now-unused function.
Fix whitespace.
Prepare DJ_MP_RATE for slaughter (gammafunk)

Move it to player.cc (the only place it is used), make it a constant
instead of a macro, and put it in a TAG_MAJOR block.
Make ego qstaves less rod-like (Brannock)
Fix a shadow
Allow specifying a default to choose_god.
Prompt for a god with &W(rath).

Defaulting to your current god.
Display monster magic immunity again

Kind of lonely-looking, tbqh; bikeshedding suggestions welcomed!
Improve sewer merfolk adjectives (simmarine)
Fix a sickly description
Fix a malarious description.

And swap clauses around.
Improve a wizmode message and comment.
Make FULLDEBUG less spammy by default