Fix Build Breakage of Antenna Track Plugin with QT 5

The Antenna Track Plugin has not been maintained for a long time, and it won't compile with QT 5. This fix will eliminate the build errors.
Changes:
1. Fix dependencies of the Antenna Track plugin.
2. Replace QextSerialPort libraries with QT 5 built-in serial port libraries.
3. Use new macros to register this plugin.
4. Enable the plugin by default.

Reported-by: Ye Wang wangyeee@gmail.com
Fix issues found in code review.

1. Remove codes which have been commented out.
2. Use new methods in QT 5.
3. Add Tau Labs as author in source file headers.
Merge pull request #1213 from wangyeee/next

Fix Build Breakage of Antenna Track Plugin with QT 5
Merge remote-tracking branch 'upstream/next' into draco
OSD: stopwatch are now paused when throttle is low