* fix issue of 'Error writing to QHostAddress("")'

(cherry picked from commit 9450b97c94af8c4919151ae91e9c7601b74e95ad)

* remove obsolete comments

(cherry picked from commit 7ff3b0049b9f91f39f5e764c92058ba1c0484308)

* add comment on why the additional condition check is required.

(cherry picked from commit 149e19b7c90f178f8a7e8a544243ce7acd642fe8)

* Remove unneeded mutex

* Cleanup LinkInterface, fix connect/disconnect bug

New VehicleLinkManager implementation

Cherry pick UDPLink range for fixes from Stable

Add mutex for _sessionTargets access. Remove range_for usage. General cleanup

Added a transmitOnly flag to UDP config. When enabled, the socket receive buffer is set to zero such that no data is ever received. Also updated the MavlinkSettings page such that new config settings respect the setting visibility.

Updated mavlink forwarding implementation to forward all mavlink messages received on all channels onto a single UDP port. A new mavlink forwarding UDP link is created if forwarding is enabled. The mavlink settings page now has a Fact checkbox for enabling forwarding and a fact text field for specifying the host name.

To have both order from the GCS and drone messages in logs
So that it's possible to analyze the complete exchange between QGC and the
drone.

- Add a signal emitted by writeBytes of each LinkInterface
- Connect this signal to MAVLinkProtocol::logSentBytes in LinkManager
- MAVLinkProtocol::logSentBytes will parse and log messages sent from
  QGC

qobject_cast is times faster dynamic_cast for objects that
inherit QObject. also, use auto keyword to not duplicate
class names.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Work around a new Windows issue where the call to list the local network interfaces takes for freaking ever to return, blocking the UDP thread altogether.

Maintain a list of address/port pairs instead of a address/port map.

Prevent shutdown ordering crashes

This mechanism automatically queues data into the correct thread where necessary, otherwise the method is invoked directly with low overhead.

At the same time remove the UDP socket event workaround. It is not a problem.

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

There are many ways of iterating over lists in C++/Qt.
In the specific case of QStrings, it is known [1] that using
foreach with const references avoids the creation of new
QString objects in each iteration, reducing the time consumed
by the loops.

[1] https://blog.qt.io/blog/2009/01/23/iterating-efficiently/Signed-off-by: Anselmo L. S. Melo <anselmo.melo@intel.com>