gnu: Use version-major+minor in gnome and gtk.

gnu: Use version-major+minor in gnome and gtk.

* gnu/packages/gnome.scm (gnome-desktop, gnome-doc-utils,
  libgnome-keyring, evince, gsettings-desktop-schemas,
  gnome-icon-theme, libnotify, lipeas, glade, libcroco, libgsf,
  librsvg, libidl, orbit2, gconf, gnome-mime-data, gnome-vfs,
  libgnome, libart-lgpl, libgnomecanvas, libgnomeui, libglade,
  libgnomeprint, libgnomeprintui, libbonoboui, goffice, gnumeric): Use
  version-major+minor.
  (shared-mime-info, hicolor-icon-theme): Wrap long uri lines.
* gnu/packages/gtk.scm (atk, pangox-compat, gtksourceview, gdk-pixbuf,
  at-spi2-core, at-spi2-atk, gtk+-2, gtk+, pangomm, atkmm, gtkmm,
  gtkmm-2): Use version-major+minor.