Remove base max MP adjustment.

Only the 2 MP tutorial bonus used it; combine that with the max MP
decrease from self-restoration and device recharging.
Show divine/cond. shield in % and @ (Kramin, PleasingFungus)

This also changes the wizmode name from "condensation shield"
to "icy shield".
Don't veto every O/S/M/A level with a primary vault.
Refactor _print_stats_wp()
Correct a comment
Make rPois a bit more consistent (for players)

Direct damage resistance from 50% to 66%. Chance of preventing
poison from 90% to 66%. Chance of preventing curare from 80% to
66%. AF_STRONG_POISON (eg redbacks) no longer pierces rPois for
players. Wasps (AF_PARALYSE) now have their effects downgraded
one level by rPois (para -> slow, slow -> nothing) instead of
outright negated.

rPois should be a helpful resist to have, not a binary pass-fail
check for certain areas & enemies.
Improve torpor snail sprite slighty
Refactor ballisto_on_move()

Also change message printing behaviour slightly; it's now
possible to get "a ballistomycete grows in the wake of something",
which is strange, but not necessarily wrong.
Move held_status() from stuff.cc to traps.cc

Also add some comments to stuff.h, categorizing functions for
later removal.
Move get_ch() from stuff.cc to macro.cc
Move cio_init() from stuff.cc to startup.cc

The only place it was called.
Move canned_message() from stuff.cc to message.cc
Create prompt.cc
Fix debug compilation
Staticify.
Move move_stairs() from misc.cc to melee_attack.cc

The only place it was used.
Remove an unused function

This was moved to random.cc in 2009 (!), but the old definition
in stuff.cc seems to have been overlooked.
Restore div_round_up()

I hadn't thought to check if it was actually *defined* in
random.cc, so of course it was not. For five years, declared in
random.h and defined in stuff.cc.
Add end.cc
Fix compilation (johnstein)