About libxfconf-1 version bump of xfconf 4.13.0

[Ali Abdallah]

Hello,

As you may have seen already,a development version of xfconf
4.13.0 has been released. This release required me to bump libxfconf
version from 0 to 1 (see the announce mail).

I invite package maintainers to start linking to the new library. All
you need to do is to replace your XDT_CHECK_PACKAGE for xfconf so it 
looks like:

XDT_CHECK_PACKAGE([XFCONF], [libxfconf-1], [4.13.0]) 

and you are okay to go. 

Unfortunately some packages have decided to hard code XFCONF_TYPE_G_VALUE_ARRAY
(which is a dbus_g_type_get_collection ("GPtrArray", G_TYPE_VALUE))
Of course this needs to be changed to GPtrArray/G_TYPE_PTR_ARRAY. But apart 
from that no modifications are required. 

I can recall some places where it is declared as above:

* xfce4-settings in xfsettingsd/pointers.c:50  #define  XFCONF_TYPE_G_VALUE_ARRAY ....
* and in xfce4-panel in common/panel-xfconf.c and common/panel-dbus.h

I can take care of the panel since I'm porting it to gdbus instead of
the deprecated dbus-glib library. 

Regards,
Ali