Direct UDisks support for libfm and pcmanfm is finished!

I just finished direct udisks support for libfm and pcmanfm. After days of testing, it works well. So it’s now merged back t master branch and will be available in next release of libfm.  Please help test it.
Nothing in pcmanfm need to be changed. You only need to update libfm and it works. Adventurous users are encouraged to try out the latest libfm in git repository.

In addition, I add a config value in libfm.conf.
Adding show_internal_volumes=1 to [config] section of
~/.config/libfm/libfm.conf can let you show system internal volumes in
side panes even when udisks asks us to hide them.
This option is available in config file, but this might not be provided in UI later since it’s a geek’s option.

Now, gvfs is not needed for volume management. Only dbus and udisks are needed and it’s quite lightweight.
However, due to known limitations of glib/gio/gvfs, the gvfs module doing volume management still gets loaded and there is no clean way to stop it being loaded. However, if later we finished our own gvfs implementation, you won’t need gnome gvfs and this will be solved.

P.S.: If you get the error message “GLib-GIO-WARNING **: Extension point gio-native-volume-monitor registered multiple times”, that means you’re using a glib with too old version. Earlier versions of glib causes this bug. It’s fixed in newer glib versions.