Shrink struct vectorlike_header to the only size field.

Shrink struct vectorlike_header to the only size field.
* lisp.h (enum pvec_type): Avoid explicit enum member values.
Adjust comment.
(enum More_Lisp_Bits): Change PSEUDOVECTOR_SIZE_BITS and
PVEC_TYPE_MASK to arrange new bitfield in the vector header.
(PSEUDOVECTOR_REST_BITS, PSEUDOVECTOR_REST_MASK): New members.
(PSEUDOVECTOR_AREA_BITS): New member used to extract subtype
information from the vector header.  Adjust comment.
(XSETPVECTYPE, XSETPVECTYPESIZE, XSETTYPED_PSEUDOVECTOR)
(PSEUDOVECTOR_TYPEP, DEFUN): Adjust to match new vector header
layout.
(XSETSUBR, SUBRP): Adjust to match new Lisp_Subr layout.
(struct vectorlike_header): Remove next member.  Adjust comment.
(struct Lisp_Subr): Add convenient header.  Adjust comment.
(allocate_pseudovector): Adjust prototype.
* alloc.c (mark_glyph_matrix, mark_face_cache, allocate_string)
(sweep_string, lisp_malloc): Remove useless prototypes.
(enum mem_type): Adjust comment.
(NEXT_IN_FREE_LIST): New macro.
(SETUP_ON_FREE_LIST): Adjust XSETPVECTYPESIZE usage.
(Fmake_bool_vector): Likewise.
(struct large_vector): New type to represent allocation unit for
the vectors with the memory footprint more than VBLOOCK_BYTES_MAX.
(large_vectors): Change type to struct large_vector.
(allocate_vector_from_block): Simplify.
(PSEUDOVECTOR_NBYTES): Replace with...
(vector_nbytes): ...new function.  Adjust users.
(sweep_vectors): Adjust processing of large vectors.
(allocate_vectorlike): Likewise.
(allocate_pseudovector): Change type of 3rd arg to enum pvec_type.
Add easserts.  Adjust XSETPVECTYPESIZE usage.
(allocate_buffer): Use BUFFER_PVEC_INIT.
(live_vector_p): Adjust to match large vector.
* buffer.c (init_buffer_once): Use BUFFER_PVEC_INIT.
* buffer.h (struct buffer): Add next member.
(BUFFER_LISP_SIZE, BUFFER_REST_SIZE, BUFFER_PVEC_INIT):
New macros.
(FOR_EACH_BUFFER): Adjust to match struct buffer change.
* fns.c (internal_equal): Adjust to match enum pvec_type change.
(copy_hash_table): Adjust to match vector header change.
* lread.c (defsubr): Use XSETPVECTYPE.
* .gdbinit (xpr, xbacktrace): Adjust to match vector header change.
(xvectype): Likewise.  Print PVEC_NORMAL_VECTOR for regular vectors.
(xvecsize): New command.