whatis_coord - rename 'getpos_coord' option

Rename the option for adding coordinates to autodescribe feedback for
the '/' and ';' commands from 'getpos_coord' to 'whatis_coord', after
the '/' command that uses it instead of after the internal routine
that implements it.  The 'whatis' name was only in dat/hh as far as I
could find, so this changes it to 'what-is' and also updates dat/help
and the Guidebook to mention the name too.

Add a 'screen' choice to the option to show coordinates as row,column
rather than x,y or compass direction(s).  Revise the /m, /M, /o, /O
operations of 'what-is' to honor the whatis_coord option (mostly; a
value of 'none' gets overridden by 'map' to force coordinates).

Also, update the description of the functionality of the '/' command
in the Guidebook.  The .mn version is tested, the .tex one isn't.

dat/opthelp

@@ -157,6 +157,13 @@ suppress_alert disable various version-specific warnings about changes
               for the 'Q' command that quitting is now done via #quit
               (e.g., use suppress_alert:3.3.1 to stop that and any other
               notifications added in that version or earlier) default: [(none)]
+whatis_coord  controls whether to include map coordinates when autodescribe
+              is active for the '/' and ';' commands.  Value is the first
+              letter of one of
+              compass -- ('east' or '3s' or '2n,4w')
+              map     -- <x,y>        (map column x=0 is not used)
+              screen  -- [row,column] (row is offset to match tty usage)
+              none    -- no coordinates shown; default: [n]
 
 Compound options which may be set only on startup are: