osc: output control signals

[jean-emmanuel]

This PR addresses the features mentioned in #3 by doing the following changes:

• create signals for output controls
• update signals values when a query is received (message with no value) before sending the reply
• add output control for meter level (returns the loudest channel's level)

It doesn't update nor send feedback for output signal on every value change because it may happen at a very high rate and there's no throttling mechanism (although some comments in the code indicates there had been plan to implement one). So far this simple query approach worked just fine for me.

[jean-emmanuel]

I tried to explain the changes I made (best viewed here), please tell me if something is not clear.

[Stazed]

Two minor issues:

Module::Port::osc_control_update_signals ( void *user_data )

missing :

Fl:lock()

at the beginning of the function.

And:

Meter_Module::update ( void )

Getting a compiler warning about misleading indentation:

// use loudest channel for public meter level
if ( v > dB )
    dB = v;

I tested what I can and it seems like everything I use is still working :). So if you can make the above changes, I will merge this.

[jean-emmanuel]

Done, thanks for the review

[jean-emmanuel]

I just fixed a typo and a segfault case I had overlooked.