fix #H2225 - death by poison after life-saving (trunk only)

From a bug report,
when falling into a spiked pit and being killed and then life-saved, you
could immediately die from fatal poison.  It isn't necessarily a bug and
there are other ways to be killed, life-saved, and re-killed (such as
zaps that bounce off walls or reflecting targets), but it does seem to be
somewhat unfair.  This patch makes life-saving be more effective:  in a
damage-plus-poison situation, if the damage triggers life-saving then the
poison won't deal out any further damage (including its nasty chance for
instant death).  The poison still matters, but it will always target an
attribute stat--which is already one possible random outcome--instead of
maybe doing damage.  [It is actually possible to get damage if stat loss
tries to take hero's strength below 3, but now there's no chance of that
being fatal immediately after savelife() has restored full hit points.]

doc/fixes35.0

@@ -343,6 +343,8 @@ when reading an unknown scroll and learning it, discovery of teleporation was
 using an unlocking tool on a closed door which was actually a mimic reported
 	that there was no door to unlock instead of exposing the mimic
 purple worm could end up in wall or solid rock when swallowing ghost or xorn
+enhance life-saving by preventing subsequent poison from being fatal upon
+	rescue from death due to spiked pit, dart trap, or poisoned missile
 
 
 Platform- and/or Interface-Specific Fixes