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, disable the bogus GCC warnings, so that
there's no need for inttype_is_signed and for calling TYPE_SIGNED.
* 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'.