GTK-3 API changes

Other projects define this too; in previous versions it was simply ignored
because $Id$ was only generated by SVN checkout.

Commit de3d7f02 "Display warning if AC_PROG_INTLTOOL is used (bug #8930)"
prints a warning with a hardcoded libtool version. This patch replaces
the hardcoded value with the version number defined in configure.ac.in,
so developers will use the proper requirements.

xfce-mcs-manager has long been archived and replaced by xfconf.

This check is only for old panels (<=4.1.90) and useless today.

* automake-1.11
* autoconf-2.60
* libtool-2.4
* glib-2.30
* xfce4-panel-4.9

Update copyright dates, remove subversion $id strings, update .gitignore.

Depending on files generated during build via $(srcdir) breaks builds
that take place outside the source directory. This commit fixes one such
mistake in scripts/Makefile.am that refers to $(srcdir)/xdt-autogen.in.

Similar to AC_PROG_LIBTOOL, which has been replaced with LT_PREREQ
and LT_INIT, AC_PROG_INTLTOOL has been replaced with IT_PROG_INTLTOOL.
This commit makes xdt-autogen recommend intltool >= 0.35.0 and displays
a warning if AC_PROG_INTLTOOL is still being used in a configure script
template.

Original patch by Samuli Suominen <ssuominen@gentoo.org>

This gives warnings with full debug builds on recent gcc versions.

This disables the g_return_ macros, and quite often
we rely on that. So for the sake of stability, disable
those.

Use AUTOCONF_VERSION for automake-$ver, ACLOCAL_VERSION for
aclocal-$ver, AUTOMAKE_VERSION for automake-$ver and
AUTOHEADER_VERSION for autoheader-$ver.

This removes the custom checks for the //newest// binary
version, which gets constantly outdated.

Support LT_PREREQ as the new alternative of AC_PROG_LIBTOOL. If
the latter is used, show a message with information how to switch
to LT_PREREQ.

Mike Massonnet authored Aug 27, 2011 and Nick Schermer committed Sep 08, 2011

The translations have been removed from the code -- Nick.

Use the macro shipped with pkg-config for detection of
$PKG_CONFIG. This to fix cross-build compatibility.