Improve build templates by not having to set ${triggers} in some cases.

There's no need to update triggers in the following cases:
 * Packages installing stuff into /usr/share/applications.
 * Packages setting $gtk_iconcache_dirs.
 * Packages setting $font_dirs.
 * Packages setting ${sgml,xml}_entries.

--HG--
extra : convert_revision : 11c74b41f8cf474e9bf4dbb961b1aa9c6f6540bf

srcpkgs/xfce4-panel/template

@@ -18,7 +18,6 @@ conf_files="/etc/xdg/xfce4/panel/launcher-7.rc
  /etc/xdg/xfce4/panel/launcher-10.rc
  /etc/xdg/xfce4/panel/clock-14.rc"
 gtk_iconcache_dirs="/usr/share/icons/hicolor"
-triggers="gtk-icon-cache"
  
 subpackages="$pkgname-devel"
 Add_dependency build pkg-config