otransit_msg() fixes

Fixes #156

githib issue #156 complains that "The Excalibur falls down the stairs,"
is using poor grammar despite the fact that the usual drop message is
"You drop the +0 Excalibur."  I agree.  Change it to be "Excalibur
falls down the stairs."  (Drop message remains unchanged.)

While looking at that, I noticed that when knocking other items down
stairs, text was being appended to the formatted object name.  It was
probably safe due to the space reserved for inserting a prefix while
formatting an object's name, which becomes available for a suffix
after that name has been copied into otransit_msg()'s local buffer,
but using a separate buffer is safer.

doc/fixes36.2

@@ -189,6 +189,9 @@ fix odd wording "The boulder triggers and fills a pit"
 ^X status feedback: don't report "not wearing any armor" when wearing a shield
 attempting to #ride a long worm's tail could trigger impossible "worm_cross
 	checking for non-adjacent location?"
+avoid "The " in "The <known-artifact-but-not-The-artifact> falls down stairs."
+avoid potential buffer overflow if object with very long name knocks other
+	objects down stairs when dropped, thrown, or kicked there
 
 
 Fixes to Post-3.6.1 Problems that Were Exposed Via git Repository