Update submodule v2.0 to latest Mon Dec 3 00:37:56 UTC 2018

    - v2.0 in PX4/Firmware (2923e40d8777ccf2581d888f8e41a48dfa93f09d): https://github.com/mavlink/c_library_v2/commit/7c47254ddc8bf70eb5e82b4c2142a3faa4fa5780
    - v2.0 current upstream: https://github.com/mavlink/c_library_v2/commit/c38176a0a63556815ea117c6877ce2dd18739231
    - Changes: https://github.com/mavlink/c_library_v2/compare/7c47254ddc8bf70eb5e82b4c2142a3faa4fa5780...c38176a0a63556815ea117c6877ce2dd18739231

    c38176a 2018-11-30 PX4BuildBot - autogenerated headers for rev https://github.com/mavlink/mavlink/tree/4c160eac64675b87f7000a9a352654182ebcfba6
057bcc4 2018-11-30 PX4BuildBot - autogenerated headers for rev https://github.com/mavlink/mavlink/tree/113731eaaf53c6cd725eb973c7cc923aa43e9c23
b1aa2b8 2018-11-29 PX4BuildBot - autogenerated headers for rev https://github.com/mavlink/mavlink/tree/8349b1cf68565c249cbad8aae0db0a466478b6a5
c3ba3f9 2018-11-29 PX4BuildBot - autogenerated headers for rev https://github.com/mavlink/mavlink/tree/5e539462241d8a088619e842c72e8030c134ab0c
077265a 2018-11-28 PX4BuildBot - autogenerated headers for rev https://github.com/mavlink/mavlink/tree/62fa8289790696a59569a79461c88f8ecb45c5ac

v2.0 @ c38176a0

-Subproject commit 7c47254ddc8bf70eb5e82b4c2142a3faa4fa5780
+Subproject commit c38176a0a63556815ea117c6877ce2dd18739231