Given the changes to thrown Loadstones, monsters should throw them at you whenever they have one.
Left this out of the Loadstone-throwing update commit
Meging in some features from SLASH'EM: Wands of Draining, Amulets of Drain Resistance, Deep Dragons, Displacer Beasts, Shimmering Dragons, and made their changes to dragon stats

Also added (temporary) intrinsic drain resistance and (temp) intrinsic displacement, as well as intrinisc acid resistance

mondata: defined macros for monster drain resistance and displacement. Shimmering dragons have displacement in dnethack.

monflag: added MR_drain flag, there should still be room in the variable used to track MR flags, so tacked on a zero for consistency's sake

youprop: Fixed mistaken conflation of intrinsic acid resistence and intrinsic poison resistance. Defined trackers for intrinisic displacement. Displacment now takes into account polymorph form also

apply.c: Merged in wand of draining effects, also merged in wand of teleportation break effects

cmd.c: Added drain resistance, acid resistance, and displacement to the list of things you can get clues about through self-consideration (Ctrl^x) without enlightenment.

do_wear.c: meged amulet of drain resistance

eat.c:
-Eating a monster that grants Acid resistance conveys temporary acid resistance
-Eating a monster that has displacement can grant temporary displacement.
-Temp displacement lasts a number of turns = nutritional value of monster. It is not modified by the difficulty of the monster
-Fixed a mistake that used !TIMEOUT to clear the timer bits instead of ~TIMEOUT (~ is bitwise not, ! is logical not)
-Fixed a mistake where the "permanent" flag was not properly used for most intriniscs
-Eating an amulet of drain resistance grants intrinisc drain resistance for 1000 turns.
-Eating a deep dragon grants a free level (not drain resistance!)

engrave.c: Merged in Wand of draining

exper.c: Substituted a call to resists_drli() to a check of Drain_resistance (which takes into account resists_drli AND other factors)

hack.c: merged in handling of monster displacement

mhitu.c: tweaked handling of life drain attacks. Made vampire life drain more common, fixed a potential notification bug in Demogorgon's gaze changed resists_drli calls to Drain_resistance checks

mon.c: Undeffered shimmering dragon, added deep dragon

mondata.c: added deep dragon growth, undefered shimmering dragon

monst.c:
-Gelatinous cubes grant temporary acid resistance as well
-Added displacer beast. Note that displacer beasts have flying in dnethack, they can't be killed through displacement onto lava or water.
-Reduced baby dragon levels and offensive capabilities.
-Increased adult dragon levels, including the Chromatic Dragon's
-Undefered shimmering dragons. Shimmering dragon attack changed to random breath, meaning they loose magic resistance but gain disintegration potential.
-Added deep dragons. Deep dragons have more level-draining attacks than in Slash'em.

muse.c: Added use of wand of draining and wand of cancellation. Added flag for scroll of earth but didn't add handling.

objects.c: Undefered shimmering dragon mail and scales, added deep dragon scales and mail, merged in amulet of drain resistance and wand of draining

polyself.c: Undefered shimmering dragon, added deep dragon.

timeout.c: added messages for acid resistance, drain resistance, and displacment

zap.c: added handling of wand of draining

monsters.txt: merged tiles for new monsters

objects.txt: merged tiles for new objects

tilemap.c: undefered Shimmering dragons and their scales and mail.