GitHub issue #1254

> If there's a trap on a no-dig level, the floor beneath it will always be "too hard to dig into", making it impossible to remove the trap.
>
> As you can still dig pits in these levels (just not holes), the floor under the trap itself resisting to become a pit seems inconsistent.
>
> Steps to reproduce:
>
> Go to no-dig level like Mine's End
> Make a trap
> Dig a pit next to it -> works
> Dig on the trap -> does not work

Return more information about the dig_check() results to caller (was
just a boolean).

Move the messaging that was in dig_check() into a separate
digcheck_fail_message() function that uses the expanded return
information.

Resolves #1254

.

include/extern.h

@@ -498,7 +498,9 @@ extern int wiz_mgender(void);
 extern int dig_typ(struct obj *, coordxy, coordxy);
 extern boolean is_digging(void);
 extern int holetime(void);
-extern boolean dig_check(struct monst *, boolean, coordxy, coordxy);
+extern enum digcheck_result dig_check(struct monst *, coordxy, coordxy);
+extern void digcheck_fail_message(enum digcheck_result, struct monst *,
+                                  coordxy, coordxy);
 extern void digactualhole(coordxy, coordxy, struct monst *, int);
 extern boolean dighole(boolean, boolean, coord *);
 extern int use_pick_axe(struct obj *) NONNULLARG1;