Handle LISP_WORDS_ARE_POINTERS and CHECK_LISP_OBJECT_TYPE.

Handle LISP_WORDS_ARE_POINTERS and CHECK_LISP_OBJECT_TYPE.

* src/comp.c: Introduce the Lisp_X, Lisp_Word, and Lisp_Word_tag
types. These types are used instead of long or long long. Use
emacs_int_type and emacs_uint_types where appropriate.
(emit_coerce): Add special logic that handles the case when
Lisp_Object is a struct. This is necessary for handling the
--enable-check-lisp-object-type configure option.

* src/lisp.h: Since libgccjit does not support opaque unions, change
Lisp_X to be struct. This is done to ensure that the same types are
used in the same binary. It is probably unnecessary since only a
pointer to it is used.