losing saddle while riding

Noticed while looking at something else:  zapping a wand of opening
or spell of knock downwards while riding causes your steed's saddle to
fall off, which in turn causes the hero to fall and take some damage.
If that damage was fatal, the saddle would be left worn in bones data.
This reorganizes mdrop_obj() to defer until last the part that ultimately
makes the hero fall off, and changes bhitm() to call that instead of
handling saddle removal inline, also gives new saddle-off feedback there.

doc/fixes34.4

@@ -346,6 +346,7 @@ make quest leader and nemesis be unlikely to be affected by traps
 use a more precise jumping path for far, non-straight line destinations
 increase damage bonus applies when kicking while polymorphed into a monster
 	form which has a kicking attack, just like for other kicks
+if magically removing steed's saddle is fatal, don't leave it saddled in bones
 
 
 Platform- and/or Interface-Specific Fixes