fix github issue #148 - life-save while swallowed

Life-saving was setting u.uswldtim to 0, presumably intending that
to stop the hero from being digested, but it actually resulted in
being totally digested on the swallower's next turn if the death
being short-circuited wasn't digestion.  Change life-saving to make
swallower or grabber release the hero instead of tinkering with
u.uswldtim.  In addition to rescuing the hero from digestion, it
prevents an eel which has just drowned the hero (who has survived
drowning via life-saving) from pulling him/her back into the water
on its next turn.  It will need to make another successful grab to
do that now.

While testing, I noticed that if I was polymorphed and wearing an
amulet of unchanging, life-saving didn't restore my HP-as-a-monster
and due to the recent change to force that to 0 when the hero dies,
I died again immediately after my life was saved.  So this bug was
latent in the past and became noticeable in the last couple of days.

doc/fixes36.2

@@ -191,6 +191,7 @@ make long extended commands list be more navigable
 simplify #wizidentify; don't rely on having bold menu entries
 ensure tmp_at() structures are initialized for all code paths when swallowed
 trapped-vs-levitation/flying change broke Sting releasing hero from web
+life-saving while poly'd and Unchanging wasn't restoring u.mh (HP as monster)
 tty: turn off an optimization that is the suspected cause of Windows reported 
 	partial status lines following level changes
 tty: ensure that current status fields are always copied to prior status
@@ -274,6 +275,7 @@ make mine town "orctown" variation a multiple level feature of the mines
 replace #monpolycontrol command with monpolycontrol boolean option
 replace #wizdebug_traveldisplay command with travel_debug boolean option
 rename #wizdebug_bury command to #wizbury
+life-saving now makes swallower or grabber release hero
 
 
 Code Cleanup and Reorganization