r45509 snapshot

Gtk3: Add label "Master volume" in front of volume slider

In the settings node "Audio" -> "Sound driver", add a label next to the volume
slider to avoid confusion for certain citrus people.


git-svn-id: https://svn.code.sf.net/p/vice-emu/code/trunk@45509 379a1393-f5fb-40a0-bcee-ef074d9b53f7