fix #2382 - temp Dex loss becomes permanent when dismounting

From a bug report, if you dismount
from a steed whose legs are wounded, you won't recover the point of
dexterity which was removed when they becme injured.  He noticed the
case where the steed had just died, but it happens for voluntary
dismount too (actually any dismount except one which wounds the hero's
legs in the process:  DISMOUNT_THROWN or DISMOUNT_FELL).

     It seems rather odd that the hero temporarily loses Dex when the
steed becomes injured, but I haven't changed that.

doc/fixes34.4

@@ -407,6 +407,8 @@ for number_pad:2 (MSDOS compatibility), M-5 (Alt+5, or Shift+keypad5 using
 objects inside the Wizard's Tower can't be teleport to outside and vica versa
 unlit candelabrum would become unlightable if its candles had exactly 1 turn
 	of fuel left and it was applied anywhere other than the invocation spot
+temporary loss of Dex from wounded legs will become permanent if it occurs
+	while mounted and hero dismounts before steed's legs have healed
 
 
 Platform- and/or Interface-Specific Fixes