inttostr: simplify by removing unnecessary redundancy

inttostr: simplify by removing unnecessary redundancy

* lib/anytostr.c: Don't include verify.h.
(anytostr): Don't verify that TYPE_SIGNED (inttype) equals
inttype_is_signed.  Instead, use TYPE_SIGNED (inttype) directly.
This removes the need for inttype_is_signed, which was put in to
suppress some GCC warnings about conversions.  This rewrite should
also suppress those warnings.
* lib/imaxtostr.c (inttype_is_signed): Remove; no longer needed.
* lib/inttostr.c, lib/offtostr.c, lib/uinttostr.c, lib/umaxtostr.c:
Likewise.
* modules/inttostr (Depends-on): Remove 'verify'.