Bug#1120607: No longer supports XPM, needed by various programs

[Benjamin Gilbert]

Package: libgdk-pixbuf-2.0-0
Version: 2.44.4+dfsg-2
Severity: important

gdk-pixbuf 2.44.4+dfsg-2, currently in experimental, switched to
Glycin and removed all non-Glycin loaders, including for several
formats Glycin doesn't support yet:

- ANI (Windows animated cursors)
- ICNS (an older macOS icon format)
- QTIF (old QuickTime container format for still images)
- XBM (pre-X11 one-bit X bitmaps)
- XPM (X11 bitmaps)

Most of these are fairly obscure, but many older X11 programs ship
icons or other image assets in XPM format and expect gdk-pixbuf to
load them.  With 2.44.4+dfsg-2, some of these (like claws-mail) report
errors and continue without the images, and some (like xsane) crash at
startup.

There's an upstream Glycin bug [1] to add XPM support.  Meanwhile, I'd
recommend building gdk-pixbuf with -Dothers=enabled and then removing
the resulting modules except for XPM.

[1]: https://gitlab.gnome.org/GNOME/glycin/-/issues/192