Get rid of a lot of references to secret doors.
Remove "magical" from dragon armour description.

It did require magic for its making, as you don't lug a whole set of
leatherworking tools with you -- especially ones capable of working with
hide stronger than steel, but its shape aside, it's no different from
hide it was made from.
Don't claim that potions of decay "start" rot.

Everything goes in a single chunk immediately.

Also, eliminate a weird special case that would stop the messages once you
accumulate 40 points of pending rottage.
Tweak wording.
Update release docs a bit.

Especially the thing about -O2 being faster than higher levels, it's long
since untrue, and -Ofast gives a huge boost with gcc-4.7.
A new themed vault, Lightli's fault.

I changed its orientation as it looks odd in the middle of a level.
When a skill reach level 27, also disable training it in the "other" mode.

Other mode being either auto or manual depending on which one is active.
Probably the cause of #6507. It's only a display bug by the way, level 27
skills are never trained.
Fix a crash on placing some bad zombies (blackcustard)

If, in an attempt to pick a base monster for the zombie, a M_NO_POLY_TO
one was chosen, the loop for some reason took it as valid.

This commit also makes this function more readable.
Add formatting fixes.
Abyss Exit Probability

Abyss Exits become more frequent the deeper you get.
At Abyss:5 exits should be approximately 3x more common then at Abyss:1.
As before, having the rune makes exits ~7x more common than Abyss:1 (regardless of level).
Constify.
Make debug mode Abyss not so extremely spammy.
Give debug abyssal messages a separate dprf class.

(We still lack an interface to toggle such classes, though.)
Give monster placement debug messages their own class.
A basic interface for manually togging dprf quietness.
Formatting nazi to the rescue!
Revert "Abyss Exit Probability"

This reverts commit ea0574a2872b6c77aca3042ee5d35b9618e55c8d.

The logic was reversed; _abyss_exit_chance() gets fed to a one_chance_in(),
so larger values mean smaller chance of an exit.
A simpler formula for abyss exit frequency.
Use "Killed by" prefix when displaying long form of direct Xom deaths.

This is the same fix as 61736378 for a different case that was missed at
the time; it causes direct Xom deaths to display as "Killed by the
[severe] capriciousness of Xom" instead of just "the [severe]
capriciousness of Xom".
Remove wolf spiders from Summon Swarm.

They are simply far too strong for this rod after the buffs to them for
Spider branch. Replace them with regular spiders.

Also, give monsters the same swarm distribution as players.