add vgm logging support

[djmaximum17]

it would be nice to have vgm logging output for sameboy, because MAME MESS is not very intuitive to use when it comes to ripping music from games or making music with LSDJ. the way I think it should be implemented is to have something in the menu bar for "record VGM output" with a check mark for "start logging vgm" and the check mark will disappear for "stop logging vgm" at least thats what kega fusion does. in MAME MESS you have to log the entire thing in one vgm file which is very inconvenient, and the file browser in MAME MESS is not very intuitive.