it breaks loading png icons through gdk_pixbuf_new_from_file as gtk is
linked with systemwide png. This went unnoticed so far as firefox always
shipped a fallback xpm icon, but this is not the case anymore, so now
gtk_window_set_icon_list() is not called anymore, and the window manager
shows the default icon for firefox windows in taskbar/tasklists..
So add graphics/netpbm as a build dependency, do the necessary netpbm
magic in do-install to create the default.xpm from mozicon128.png, and
patch widget/src/gtk2/nsWindow.cpp to not try to load png icons.
While here fix icon path in desktop file, and add a comment about why we
don't use systemwide png.
de100a1ff9