The OPL2LPT is an OPL2 chip plugged on a parallel port. It is
write-only but otherwise acts as a classic AdLib. This commit adds
support for this device.
User is expected to have the right permissions on the parallel
port. By default, the first suitable parallel port is used. It is
possible to override that with the hidden configuration setting
"opl2lpt_parport".
It depends on the presence of the libieee1284 library which abstracts
a bit parallel port handling. An alternative would be to access
directly /dev/parportX on Linux. This would amount of code but it
would be Linux-only.
Tested with Indy 3 and SOMI.
The way I've configured ScummVM, the default is to use FluidSynth
for MIDI, and any game where I want AdLib overrides that setting.
I have set the DOSBox OPL emulator as the default.
However, this causes the game's "opl_driver" setting to be "auto",
which overrides the default setting, and usually picks the MAME
OPL emulator. To counter this, if it sees that "opl_driver" is
"auto", it will check the default setting.
In other words, only use "auto" if "opl_driver" isn't set on any
level. I think this is the behaviour that should cause the least
amount of astonishment.
