Make PC compute glide-ratio. Configure it on EICAS.
Remove unnecessary <array> includes.
Update config - layout of EICAS.
Add alt-acquired sound.
Details.
Add support for 'altitude acquired' flag.

* Add boolean flag property to the altacq module.
* Add playing appropriate sound to the EFIS module,
  when cmd-altitude-acquired flag is set.
* Add convenience method GenericProperty::valid_and_fresh().
Doc update. And style fix.
Add "Airframe" subsystem to the Application.
Add FlapsBugs module and display flaps speed limits on EFIS.
Fix EFIS not to draw orange warning about speed.

If min/max-maneuver speed is not provided, speed box was painted
with orange rectangle improperly.
Add FlapsBugs module and configure it on EFIS.
Add the Mixer module and configure for anti adverse-yaw effect.
Update copylefts.
Add very simple yaw damper module.
Set settings that don't change in constructor.
Add tool for updating copylefts.
Use .valid_and_fresh() where possible.
Use std::abs() directly on a SI value.
Fix some issues found by clang.

Unfortunately clang's C++11 support is quite limited, so no further
diagnosis/investigation for now.
Use names VOR 1/2 instead of VOR L/R.