autodig '>'

This fixes moving in direction '>' while wielding a pick-axe with
the 'autodig' option On.  Attempting to dig assumed size-to-side
activity because u.dz wasn't being set, so the pick-axe was swung at
thin air instead making a pit or turning an existing pit into a hole.

dodown() and doup() should probably call set_move_cmd() instead of
manipulating u.dz directly.  But they would also need to suppress
g.move_attempting or the game says "you can't get there from here..."
after successfully digging or plunging into a pit.

doc/fixes37.0

@@ -980,6 +980,8 @@ changing engraving to an occupation resulted in not dulling a weapon used to
 a change to wounded legs handling resulted in not recovering lost dexterity
 	or receiving the "leg(s) feel better" message if wound time expired
 	rather than having legs be explicitly healed
+turning movement into commands interfered with using pick-axe plus autodig
+	in downward direction
 
 curses: 'msg_window' option wasn't functional for curses unless the binary
 	also included tty support