Simplify export of symbols to GDB; fix related .gdbinit bugs.

Simplify export of symbols to GDB; fix related .gdbinit bugs.

* etc/emacs-buffer.gdb ($tagmask, $valmask): Remove.
(ygetptr): Adjust to recent changes in lisp.h and emacs.c,
by using VALMASK instead of $valmask, CHECK_LISP_OBJECT_TYPE
instead of gdb_use_union, and DATA_SEG_BITS instead of
gdb_data_seg_bits.  Also, use $ptr.i rather than $ptr.u.val.
* src/.gdbinit (xgetptr, xgetint, xgettype): Don't use "set $bugfix =
$bugfix.i", as this doesn't work (with GDB 7.4.1, anyway).
(xgetptr, xgetint, xgettype, xcoding, xcharset, xprintbytestr):
Adjust to changes in lisp.h and emacs.c, by using
CHECK_LISP_OBJECT_TYPE rather than gdb_use_struct, VALMASK instead
of $valmask, DATA_SEG_BITS instead of gdb_data_seg_bits,
INTTYPEBITS instead of gdb_gctypebits - 1, USE_LSB_TAG instead of
gdb_use_lsb, (1 << GCTYPEBITS) - 1 instead of $tagmask, VALBITS
instead of gdb_valbits.
(xvectype, xvector, xpr, xprintstr, xbacktrace): Similarly, use
PSEUDOVECTOR_FLAG instead of PVEC_FLAG, and ARRAY_MARK_FLAG
instead of gdb_array_mark_flag.
(xboolvector): Get size from $->size, not $->header.size.
Use BOOL_VECTOR_BITS_PER_CHAR rather than mystery constants.
(xreload, hook-run, hookpost-run): Remove.
* src/emacs.c: Include <verify.h>.
(gdb_use_lsb, gdb_use_struct, gdb_valbits, gdb_gctypebits)
(gdb_data_seg_bits, PVEC_FLAG, gdb_array_mark_flag, gdb_pvec_type):
Remove.
(gdb_CHECK_LISP_OBJECT_TYPE, gdb_DATA_SEG_BITS, gdb_GCTYPEBITS)
(gdb_USE_LSB_TAG): New enum constants.
(CHECK_LISP_OBJECT_TYPE, DATA_SEG_BITS, GCTYPEBITS, USE_LSB_TAG):
Also define these as enum constants, so they're visible to GDB.
(ARRAY_MARK_FLAG_VAL, PSEUDOVECTOR_FLAG_VAL, VALMASK_VAL): New macros.
(ARRAY_MARK_FLAG, PSEUDOVECTOR_FLAG, VALMASK): Also define these
as constants, so they're visible to GDB.
* src/lisp.h (VALBITS, INTTYPEBITS, FIXNUM_BITS, PSEUDOVECTOR_SIZE_BITS)
(PSEUDOVECTOR_SIZE_MASK, PVEC_TYPE_MASK, BOOL_VECTOR_BITS_PER_CHAR):
Now enum constants, not macros, so they're visible to GDB.
(CHECK_LISP_OBJECT_TYPE, DATA_SEG_BITS): Default to 0, as this is
more convenient now.  All uses changed.
(VALMASK) [USE_LSB_TAG]: Also define in this case.
* src/mem-limits.h (EXCEEDS_LISP_PTR): Adjust to DATA_SEG_BITS change.