Give curses_color_attr() in-game color constants

... instead of Curses color constants, since the whole point of the
function is to convert the former to the latter.  This fixes faulty
colors with PDCurses under some circumstances.

This is meant to go with commit f5a556f501 (NH4 --More-- by screenfuls,
not by lines), commit 6800dc7570 (No-inverse name-HP bar uses black
background) and commit 6e1348de86 (Color-code turn count changes).

This bug also exists in NetHack4.
oprops: Fix "thirsty knife of drain resistance"

Dumb mistake on my part; it should just be "thirsty knife" for weapons
and weapon-tools.

This is meant to go with commit d7d07e4d60 (oprops: magical object
properties from GruntHack).