mind flayer brain attacks (trunk only)

mind flayer brain attacks (trunk only)

     Fix a couple of problems From a bug report.  Eating a Rider corpse is fatal, but eating a live Rider's
brain was not--now it will be, both for monster mind flayers and for player
poly'd into one.  Also, there was no check for cannibalism when poly'd hero
eats brains--now there is.  Not mentioned in the report:  eating Medusa's
brains will now be fatal just like eating her corpse.  And pet mind flayers
who eat the hero's brains will gain some nutrition like they do when eating
monster brains.

     Creating a common eat_brains() routine turned out to be something of
a mistake; there is only a tiny amount of overlap among the u-vs-m, m-vs-u,
and m-vs-m cases.

     Makefiles need a dependency update to add edog.h for eat.c.