Assume C89 or later.

Assume C89 or later.

* configure.in (AC_C_PROTOTYPES, AC_C_VOLATILE, AC_C_CONST)
(POINTER_TYPE, PROTOTYPES): Remove.
* admin/CPP-DEFINES: Remove NULL, const.
* lib-src/etags.c (static, const): Remove macros.
(PTR): Remove; all uses replaced with void *.  Omit needless casts.
* src/alloc.c, src/buffer.c, lisp.h: Replace POINTER_TYPE with void.
* alloc.c (overrun_check_malloc, overrun_check_realloc, xmalloc)
(xrealloc):
* buffer.c (mmap_free_1, mmap_enlarge): Omit needless casts.
* editfns.c, fns.c, gmalloc.c, insdel.c, sysdep.c, termcap.c (NULL):
* textprop.c, tparam.c (NULL): Remove.
* ralloc.c, vm-limit.c (POINTER): Assume void * works.
* regex.c (SIGN_EXTEND_CHAR): Assume signed char works.
* regex.h (_RE_ARGS): Remove.  All uses rewritten to use prototypes.
* unexelf.c (ElfBitsW): Assume c89 preprocessor or better.
* xterm.c (input_signal_count): Assume volatile works.