xfce4-screenshooter GTK3

[André Miranda]

Hi guys!
I'd like to announce the completion of xfce4-screenshooter port to GTK3:
https://github.com/andreldm/xfce4-screenshooter

So I call for tests and eventual merge to official repository.

The pending deprecations (I was told to not worry about them for now) are:
gdk_device_grab
gdk_device_ungrab
gdk_screen_get_active_window
gdk_screen_get_height
gdk_screen_get_width
gdk_window_process_all_updates
gtk_widget_get_style
soup_xmlrpc_parse_method_response
soup_xmlrpc_build_method_call

Also a sudden crash affects xfce4-screenshooter, I thought this was 
introduced by my changes, but this defect is present on current master 
but not version 1.8.2, so I guess this was a successful 1:1 port ^^
The problem is easy to reproduce, try to upload to zimagez, cancel when 
asked for credentials and you get a nice backtrace and memory map on 
your terminal. This also affects failed uploads to imgur, just pull the 
ethernet cable and try to upload.
Here are my findings, though I wasn't able to fix:

1c462a0 - Port from deprecated GValueArray to GArray
     Bug *probably* introduced here, works but parameter strings are broken.

     Crash in screenshooter_simple_job_finalize (GObject *object)
        /* release the param values */
     -  g_value_array_free (simple_job->param_values);
     +  g_array_unref (simple_job->param_values); <-- Here

     More precisely here (on the second pass):
https://github.com/GNOME/glib/blob/e5ed410c8c0fe823883b65b293fb2d9c9d12673a/glib/garray.c#L362

6de6b7e - Fix crash in GValueArray handling (#11879)
     Causes: assertion failed: (err != NULL || exo_job_is_cancelled (job))
             [1]    12539 abort (core dumped) src/xfce4-screenshooter

4569b71 - Fix crash when uploading to zimagez, followup to 6de6b7e (#11879)
     Fixes the previous crash but the current crash is already present.