Let integers use up 2 tags to give them one extra bit and double their range.

Let integers use up 2 tags to give them one extra bit and double their range.
* lisp.h (USE_2_TAGS_FOR_INTS): New macro.
(LISP_INT_TAG, case_Lisp_Int, LISP_STRING_TAG, LISP_INT_TAG_P): New macros.
(enum Lisp_Type): Use them.  Give explicit values.
(Lisp_Type_Limit): Remove.
(XINT, XUINT, make_number) [!USE_LISP_UNION_TYPE]:
(MOST_NEGATIVE_FIXNUM, MOST_POSITIVE_FIXNUM, INTMASK):
Pay attention to USE_2_TAGS_FOR_INTS.
(INTEGERP): Use LISP_INT_TAG_P.
* fns.c (internal_equal): Simplify the default case.
(sxhash): Use case_Lisp_Int.
* data.c (wrong_type_argument): Don't check against Lisp_Type_Limit any more.
(Ftype_of): Use case_Lisp_Int.
(store_symval_forwarding): Take into account the fact that Ints can
now have more than one tag.
* buffer.c (syms_of_buffer): Use LISP_INT_TAG.
buffer_slot_type_mismatch):
* xfaces.c (face_attr_equal_p):
* print.c (print_object):
* alloc.c (mark_maybe_object, mark_object, survives_gc_p): Use case_Lisp_Int.