Adds a dialog to unmount devices when using Wayland.

[bigbruno]

The dialog that confirms the unmount of devices that are in use by some program uses resources that are incompatible with wayland and generates segmentation fault. I added a check so that in case you are using wayland, another dialog that is compatible can be created.

Resolves the problem reported in: linuxmint/wayland#134

[mtwebster]

I'm not sure this is the way to fix this, or the right place.

In x11 sessions, the gnome vfs backend will show a busy dialog to prevent unmounting if a drive is in use:

This is what we should see in wayland sessions also...

[cyberknight777]

I'm not sure this is the way to fix this, or the right place.

In x11 sessions, the gnome vfs backend will show a busy dialog to prevent unmounting if a drive is in use:

This is what we should see in wayland sessions also...

Except it isn't shown and instead crashes as pointed out in the linked issue. So how are we proceeding with this?

[bigbruno]

With the modification that I implemented, in Wayland a dialog also appears informing what is in use, it is a simpler dialog, it does not detect the program icon, but it is working, while in X11 it continues exactly with the dialog that was already used.

The text is in Brazilian Portuguese because it is my native language, it is the text received through GVFS, so it is the same text of the dialog that already existed and will use the system language.