Don't destroy items with fire/cold melee magic

... because NetHack doesn't, even though having them destroy items would
arguably make them more consistent with the same forms of damage
elsewhere.  Introduced by Leon "L" Arnott's resistance patch, removed by
this commit.
Reduce monster level's effect on raw spell damage

Under the old NetHack rules, monster level 50 Asmodeus did 31d6 damage
with his AT_MAGC/AD_COLD attack, average 108, maximum 186.  With this
commit, that becomes 11d11 damage, average 66, maximum 121.

Despite the example, this commit reduces damage for all spellcasting
monsters, especially high-level ones.  Nobody noticed this problem in
NetHack because resistances nullify all of this damage, but it was a
real problem in DynaHack where resistances only halve damage.

Without this, players would feel more compelled to overprepare for
Gehennom, leading to more stash management, backtracking, and other
boring habits, and coming in range of Asmodeus without gold to bribe him
would effectively be instant death to all but the most overpowered
characters.
Show message when searching finds secret doors and corridors

The terms "secret door" and "secret passage" are consistent with the
stethoscope messages.
Allow vault guard to accept names that don't start with a letter

Somebody lost a NetHack game to this bug due to their name starting with
a number, so I'm not letting it happen in DynaHack.

This bug also exists in vanilla NetHack.
Show messages for objects that are randomly cursed

Objects will "glow brown" or "glow with a black aura" if they're
randomly cursed by e.g. the Wizard of Yendor or by sitting on a throne
with bad luck, just like the message given when dipping it into unholy
water.

As a bonus the object's BUC status will be revealed as well, again like
unholy water.