Fix typo in eng msg
Revert "Fix Glide Bar should not be visible when there is no valid start, if it is configured to show task arrival altitude."

This reverts commit 07d98ea709cadee62da912bc6b633222157ce416.
Fix glidebar not available (and showing ---) when showing T multitarget, with a real task, in FINISH mode, but with not a real valid start yet.
Add new infobox for Heading . Showing magnetic heading if available from an external instrument; otherwise showing
the estimated heading calculated internally.
correct typo in eng msg
Disable AHRS too experimental
Fix device driver LX not reading the magnetic heading if available
Fix HeadWind calculation using TAS if available. This value is shown in infoboxes.