This adds an extra check when XDT_AUTOGEN_CHECK_DOCS
is defined. This variable points to the directory that
should contain the xfce4-docs submodule.

If no submodule clone if found and autogen.sh is running
from within a git clone, it will automatically initialize
the submodule for the user, if not it will show an error
and abort xdt-autogen, since configure will abort too if
we continue because of missing makefile.am files.

This reverts commit 77d9703d.

Only use XDT_FEATURE_VISIBILITY to detect if visibility is
supported by the compiler. Setting the default visibility
to hidden will break libraries and modules that don't
set the visibility of their public function to "default".

also make the non-defaults explicit and therefore less confusing (it
worked before due to default autoconf shell-ification of the first arg,
but that's not immediately clear)

This reverts commit 90d68641.

AC_ARG_ENABLE executes the code its last parameter if the --enable flag
is not provided, not if the --disable flag is not provided. That's why
we need to set the value to "no", not to "yes".

Also don't show the --disable-debug option (with weird indentation)
because the help message already explains that there are --disable
variants for all --enable options.

This uses the m4_default() macro instead of the custom code to check
which debug level should be used as the default. $default_level was
not set when running configure with --help before.

It seems we also need to use [enable_debug=$enableval] in
AC_ARG_ENABLE() for enable_debug to be set. Tested it and it works fine.

we can't tell version ordering, but it's possible it's fine, so just
print a warning and proceed.  autogen.sh writers shouldn't depend on
particular git revisions, only on release versions, but let's soft-allow
it.

also rename some similar vars/functions for the same reason

users who wish to require a minimum version of xdt-autogen should
export XDT_AUTOGEN_REQUIRED_VERSION, set to the minimum required version
that is supported.

(Old svn revision: 30414)

(Old svn revision: 30408)

	  options when --enable-debug={yes,full} is specified.

(Old svn revision: 29924)

(Old svn revision: 29589)

	  script more portable. Properly detect changed ChangeLogs in SVN.
	  This should get rid the empty lines when committing several
	  changed ChangeLogs (bug #4716). Patch provided by Alexander
	  Toresson.

(Old svn revision: 29499)

	* configure.in.in: Bump version.

(Old svn revision: 29313)

(Old svn revision: 29243)