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.

include/extern.h

@@ -368,6 +368,7 @@ E void NDECL(heal_legs);
 
 /* ### do_name.c ### */
 
+E char *FDECL(coord_desc, (int, int, char *, CHAR_P));
 E int FDECL(getpos, (coord *, BOOLEAN_P, const char *));
 E void FDECL(getpos_sethilite, (void (*f)(int)));
 E void FDECL(new_mname, (struct monst *, int));

include/flag.h

@@ -171,6 +171,7 @@ struct sysflag {
 #define GPCOORDS_NONE    'n'
 #define GPCOORDS_MAP     'm'
 #define GPCOORDS_COMPASS 'c'
+#define GPCOORDS_SCREEN  's'
 
 struct instance_flags {
     /* stuff that really isn't option or platform related. They are