fix github issue #486 - feedback while engulfed

Issue is about monster shape changes being sensed via telepathy
while hero is swallowed, so player gets told about things that
aren't being shown on the map.  Similar situation while underwater;
only monsters in adjacent water spots are shown on the screen, but
messages about sensed monsters will continue to be given.  It isn't
limited to shape changing; lots of places include telepathy,
extended monster detection, and warning against specific types of
creatures as criteria to decide whether the hero 'sees' something
that isn't directly visible happen.

Change sensemon() to behave as if being swallowed or underwater
blocks telepathy, extended monster detection, and warning.  I
consider this to be experimental, but it needs much wider testing
than would take place if put into its own test branch.  It can be
tweaked or reversed if that turns out to be necessary.

There should be no change in behavior when not swallowed and not
underwater.  But for either of those two situations, some messages
that have been getting delivered may be different (such as using
"it" instead of sensed monster's name) or suppressed.

Fixes #486

doc/fixes37.0

@@ -465,6 +465,10 @@ contents of chests, large boxes, and ice boxes are now immune to water damage
 	chests+large boxes were always immune and ice boxes always vulnerable)
 applying an empty brass lantern in an attempt to light it reported "your lamp
 	has run out of power"; change to "your lantern is out of power"
+when swallowed or underwater, player could be told about events (such as a
+	shapechanger taking on a new form) that the hero sensed but which
+	were not shown on the screen; treat being swallowed or underwater as
+	situations which block telepathy, extended monster detection, warning
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository