- CONTEXT_MAINMENU is not actually needed, use CONTEXT_TREE which does the same actions
- (gigabeat) use vol+/- in the lists to control volume (every list!) (FS#6982 in a better way)
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@13062 a1c6a512-1295-4272-9138-f99709370657