Support for CUPS printer instances

[Michael Weghorn <m weghorn posteo de>]

Hello,

currently, GTK+ does not support CUPS printer instances which are a way
to save different sets of options for a certain printer. More
information about CUPS printer instances can be found in the CUPS
documentation [1] in the section "Creating Saved Options".

I have worked on an implementation for them and have attached patches to
bug 148184 [2].

I would be very grateful if somebody could have a look at them.

Best regards,
Michael

[1] http://www.cups.org/documentation.php/options.html
[2] https://bugzilla.gnome.org/show_bug.cgi?id=148184