Update submodule mavlink v2.0 to latest Wed Mar 6 00:38:42 UTC 2019 (#11596)

    -  mavlink v2.0 in PX4/Firmware (1a2b88ea30ae3bec38d2e9f11793042d7582506a): https://github.com/mavlink/c_library_v2/commit/f073569b746b6533c1715b0bbfed6c988444b257
    - mavlink v2.0 current upstream: https://github.com/mavlink/c_library_v2/commit/2a47f11e73eef6d817af7934692b1223d7fb434f
    - Changes: https://github.com/mavlink/c_library_v2/compare/f073569b746b6533c1715b0bbfed6c988444b257...2a47f11e73eef6d817af7934692b1223d7fb434f

    2a47f11 2019-03-01 PX4BuildBot - autogenerated headers for rev https://github.com/mavlink/mavlink/tree/747c3e73e9ad28e8011cdc5c98faf56752b1d32a

v2.0 @ 2a47f11e

-Subproject commit f073569b746b6533c1715b0bbfed6c988444b257
+Subproject commit 2a47f11e73eef6d817af7934692b1223d7fb434f