Major changes in release 1.9:

* AC_SIZEOF_TYPE generates the cpp symbol name automatically,
  and autoheader generates entries for those names automatically.
* AC_FIND_X gets the result from xmkmf correctly.
* AC_PROG_INSTALL finds OSF/1 installbsd.
* A copy of install.sh is placed in ${acdatadir}, for convenience.

Major changes in release 1.8:

** New macros:
* New macros AC_LANG_C, AC_LANG_CPLUSPLUS, AC_LANG_SAVE, AC_LANG_RESTORE,
  AC_PROG_CXX, AC_PROG_CXXCPP, AC_REQUIRE_CPP
  for checking both C++ and C features in one configure script.
* New macros AC_CHECKING, AC_VERBOSE, AC_WARN, AC_ERROR for printing messages.
* New macros AC_FIND_XTRA, AC_MMAP, AC_SIZEOF_TYPE, AC_PREREQ,
  AC_SET_MAKE, AC_ENABLE.

** Changed macros:
* AC_FIND_X looks for X in more places.
* AC_PROG_INSTALL defaults to install.sh instead of cp, if it's in srcdir.
  install.sh is distributed with Autoconf.
* AC_DECLARE_YYTEXT has been removed because it can't work, pending
  a rewrite of quoting in AC_DEFINE.
* AC_OUTPUT adds its comments in C format when substituting in C files.
* AC_COMPILE_CHECK protects its ECHO-TEXT argument with double quotes.

** New or changed command line options:
* configure accepts --enable-FEATURE[=ARG] and --disable-FEATURE options.
* configure accepts --without-PACKAGE, which sets withval=no.
* configure accepts --x-includes=DIR and --x-libraries=DIR.
* Giving --with-PACKAGE no argument sets withval=yes instead of withval=1.
* configure accepts --help, --version, --silent/--quiet, --no-create options.
* configure accepts and ignores most other Cygnus configure options, and
  warns about unknown options.
* config.status accepts --help, --version options.

** Paths and other changes:
* Relative srcdir values are not made absolute.
* The values of @prefix@ and @exec_prefix@ and @top_srcdir@ get substituted.
* Autoconf library files are installed in ${datadir}/autoconf, not ${datadir}.
* autoheader optionally copies config.h.top to the beginning of config.h.in.
* The example Makefile dependencies for configure et al. work better.
* Namespace cleanup: all shell variables used internally by Autoconf
  have names beginning with `ac_'.

More big improvements are in process for future releases, but have not
yet been (variously) finished, integrated, tested, or documented enough
to release yet.

Major changes in release 1.7:

* New macro AC_OBSOLETE.
* Bugs in Makefile.in fixed.
* AC_LONG_FILE_NAMES improved.

Major changes in release 1.6:

* New macro AC_LONG_64_BITS.
* Multiple .h files can be created.
* AC_FIND_X looks for X files directly if it doesn't find xmkmf.
* AC_ALLOCA defines C_ALLOCA if using alloca.c.
* --with-NAME can take a value, e.g., --with-targets=sun4,hp300bsd.
* Unused --no-create option to configure removed.
* autoheader doesn't change the timestamp of its output file if
  the file didn't change.
* All macros that look for libraries now use AC_HAVE_LIBRARY.
* config.status checks three optional environment variables to
  modify its behavior.
* The usual bug fixes.

Major changes in release 1.5:

* New macros AC_FIND_X, AC_OFF_T, AC_STAT_MACROS_BROKEN, AC_REVISION.
* autoconf and autoheader scripts have GNU standards conforming
  --version and --help options (they print their message and exit).
* Many bug fixes.

Major changes in release 1.4:

* New macros AC_HAVE_POUNDBANG, AC_TIME_WITH_SYS_TIME, AC_LONG_DOUBLE,
  AC_GETGROUPS_T, AC_DEFINE_UNQUOTED.
* autoconf and autoheader use the M4 environment variable to determine the
  path of the m4 program to use.
* The --macrodir option to autoconf and autoheader specifies the directory
  in which acspecific.m4, acgeneral.m4, etc. reside if not the default.
* autoconf and autoheader can take `-' as their file names, which means to
  read stdin as input.
* Resulting configure scripts can take a --verbose option which causes them
  to print the results of their tests.
* AC_DEFINE quotes its second argument in such a way that spaces, magic
  shell characters, etc. will be preserved during various stages of
  expansion done by the shell.  If you don't want this, use
  AC_DEFINE_UNQUOTED instead.
* Much textual processing done with external calls to tr and sed have been
  internalized with builtin m4 `patsubst' and `translit' calls.
* AC_OUTPUT doesn't hardwire the filenames it outputs.  Instead, you can
  set the shell variables `gen_files' and `gen_config' to the list of
  filenames to output.
* AC_DECLARE_YYTEXT does an AC_SUBST of `LEX_OUTPUT_ROOT', which may be
  "lex.yy" or "lexyy", depending on the system. 
* AC_PROGRAMS_CHECK takes an optional third arg.  If given, it is used as
  the default value. 
* If AC_ALLOCA chooses alloca.c, it also defines STACK_DIRECTION.
* AC_CONST works much more reliably on more systems.
* Many bug fixes.

Major changes in release 1.3:

configure no longer requires awk for packages that use a config.h.
Support handling --with-PACKAGE options.
New `autoheader' script to create `config.h.in' from `configure.in'.
Ignore troublesome -lucb and -lPW when searching for alloca.
Rename --exec_prefix to --exec-prefix for GNU standards conformance.
Improve detection of STDC library.
Add AC_HAVE_LIBRARY to check for non-default libraries.
Function checking should work with future GNU libc releases.

Major changes in release 1.2:

The --srcdir option is now usually unnecessary.
Add a file containing sample comments describing CPP macros.
A comment in config.status tells which host it was configured on.
Substituted variable values can now contain commas.
Fix bugs in various feature checks.

Major changes in release 1.1:

Added AC_STRCOLL macro.
Made AC_GETLOADAVG check for more things.
AC_OUTPUT argument is now optional.
Various bug fixes.