cmus 2.6.0

Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>
Add mouse support

Add option mouse=true/false

Add bind keys:
- mlb_click,
- mlb_click_selected,
- mrb_click,
- mrb_click_selected,
- mouse_scroll_up,
- mouse_scroll_down
Add conditionals to format strings
Add format_treewin, format_treewin_artist, format_trackwin_album