Introduce the bignum type

Introduce the bignum type

* src/alloc.c (mark_object): Handle Lisp_Misc_Bignum.
(sweep_misc): Call mpz_clear for Lisp_Misc_Bignum.
* src/data.c (Ftype_of): Handle Lisp_Misc_Bignum.
(Fintegerp, Finteger_or_marker_p, Fnatnump, Fnumberp)
(Fnumber_or_marker_p): Update for bignum.
(Ffixnump, Fbignump): New defuns.
(syms_of_data): Update.
* src/emacs.c (xrealloc_for_gmp, xfree_for_gmp): New functions.
(main): Call mp_set_memory_functions.
* src/lisp.h (enum Lisp_Misc_Type) <Lisp_Misc_Bignum>: New constant.
(struct Lisp_Bignum): New.
(union Lisp_Misc): Add u_bignum.
(BIGNUMP, XBIGNUM, INTEGERP, NATNUMP, NUMBERP, CHECK_NUMBER)
(CHECK_INTEGER, CHECK_NUMBER_COERCE_MARKER): New functions.
* src/print.c (print_object): Handle Lisp_Misc_Bignum.