* m4/init.m4: Require Autoconf 2.53b.

* m4/init.m4: Require Autoconf 2.53b.
* m4/header.m4 (AM_CONFIG_HEADER): Redefine using AU_DEFUN.
* m4/ccstdc.m4 (fp_PROG_CC_STDC): New AU_DEFUN.
* m4/dmalloc.m4 (fp_WITH_DMALLOC): Likewise.
* m4/lispdir.m4 (ud_PATH_LISPDIR): Likewise.
* m4/maintainer.m4 (jm_MAINTAINER_MODE): Likewise.
* m4/protos.m4 (fp_C_PROTOTYPES): Likewise.
* m4/regex.m4 (fp_WITH_REGEX): Likewise.
* m4/termios.m4: Delete.  AM_SYS_POSIX_TERMIOS is now AU_DEFUNed
in m4/obsolete.m4.
* m4/winsz.m4: Delete. AM_HEADER_TIOCGWINSZ_NEEDS_SYS_IOCTL is now
AU_DEFUNed in m4/obsolete.m4.
* m4/obsol-gt.m4, m4/obsol-lt.m4, m4/obsolete.m4 : New files.
* m4/Makefile.am (dist_m4data_DATA): Add obsol-gt.m4, obsol-lt.m4,
and obsolete.m4. Remove termios.m4 and winsz.m4.
* aclocal.in (obsolete, obsolete_rx): Remove.
(scan_configure): Don't grep for obsolete macros.
* tests/defs (AUTOUPDATE): Define.
* Makefile.am (maintainer-check): Check for misuses of autoupdate.
* tests/obsolete.test: Rewrite.  Exercize the AU_DEFUN macros from
m4/obsolete.m4.