throw-and-return for aklys

The comment I added to data.base--to explain that despite what the
short description says, an aklys wouldn't return to sender after being
thrown--was bugging me, so I've made aklyses behave like Mjollnir.
If thrown when wielded as primary weapon, it will usually return and
usually be re-wielded.  I also added a new message when either thrown
Mjollnir or thrown aklys is expected to return and fails to do so.

Most of the diff to dothrow.c is a change in indentation level.  The
amount of code needed was quite small.

Autopickup for thrown Mjollnir which had failed to return was putting
it into the quiver slot if that was empty.  Note quite an outright bug,
but it started wielded and can't be thrown if quivered, so exclude it
from the stuff that will auto-fill the quiver slot when added to invent
(post-3.6.0 issue).

dat/data.base

@@ -59,8 +59,6 @@ thonged club
 	it to be drawn back to the wielder after having been thrown.
 	It should not be confused with the atlatl, which is a device
 	used to throw spears for longer distances.
-
-	(NetHack's "aklys" is just a club and won't return if thrown.)
 ~agate ring
 agate*
 	Translucent, cryptocrystalline variety of quartz and a subvariety