Revamp the autoupdate/AC_OBSOLETE chain. All the details are

Revamp the autoupdate/AC_OBSOLETE chain.  All the details are
given in the prologue of acobsolete.m4.

* acgeneral.m4 (Prologue): Enter the `autoconf' name space.
(AU_DEFUN): New macro.

* autoupdate.m4: New file.
Disable the name spaces `autoconf', and `libm4'.  Disable libm4.
* Makefile.am: Tuned to support the changes above.

* autoupdate.sh: Model after autoconf.sh.
Can run on several files at once (for instance m4/*.m4).
Don't touch files that are up to date.
Run m4 on autoupdate.m4f instead of playing with sed.

Use AU_DEFUN.

* acgeneral.m4 (AC_LINK_FILES, AC_ENABLE, AC_WITH): Use AU_DEFUN,
remove the call to AC_OBSOLETE.
* acspecific.m4 (AC_CYGWIN32): Likewise.
* acoldnames.m4: Replaced all the definitions via `define' or
`AC_DEFUN' to use `AU_DEFUN'.