Update submodule libuavcan to latest Thu Apr 12 01:29:36 UTC 2018

    - libuavcan in PX4/Firmware (4093eb1): OpenCyphal-Garage/libcyphal@e1c9a4f
    - libuavcan current upstream: OpenCyphal-Garage/libcyphal@9a8b059
    - Changes: OpenCyphal-Garage/libcyphal@e1c9a4f...9a8b059

    9a8b059 2018-03-26 Pavel Kirienko - Merge pull request #122 from magicrub/upstream_ch_shadow_warning
f935822 2018-03-25 Tom Pittenger - rename ch to chr to avoid shadow variable in ChibiOS
1dfcaca 2018-01-04 Pavel Kirienko - README update; fixes #120
da34eae 2018-01-02 Pavel Kirienko - Added IAdHocNodeStatusUpdater
0066382 2018-01-01 Pavel Kirienko - TransferPerfCounter made noncopyable, returns counters by references
eebf0bf 2018-01-01 Pavel Kirienko - Linux SocketCAN: Missing initializer warning fix
9044cd1 2017-11-29 Pavel Kirienko - Merge pull request #119 from battlesnake/master
155c721 2017-11-29 Mark K Cowan - Removed redundant path delimiter
934cc4f 2017-11-29 Mark K Cowan - Fixed unnecessary sign conversion
e2c68be 2017-11-27 Pavel Kirienko - STM32: new config parameter UAVCAN_STM32_TIMX_INPUT_CLOCK
2d02258 2017-11-26 Pavel Kirienko - STM32: fixed an implicit conversion warning
ba9af4c 2017-11-24 Pavel Kirienko - Merge pull request #117 from battlesnake/master
e797d69 2017-11-24 Mark K Cowan - Fixed failing build when socket.h adds flexible arrays to end of structures.
a1022b0 2017-11-24 Pavel Kirienko - Merge pull request #115 from UAVCAN/stm32-acceptance-filter-fix
414a2e2 2017-11-21 Pavel Kirienko - Fixed the CAN acceptance filter initialization in the STM32 driver
fa6dbde 2017-11-21 Pavel Kirienko - Merge pull request #114 from daniel-formlabs/dont-overwrite-cmake-cxx-flags
337fdff 2017-11-20 Daniel Willenson - Don't completely overwrite the CMAKE_CXX_FLAGS
d577c58 2017-10-05 Pavel Kirienko - Merge pull request #113 from partyzzzan/chibi-version
60ea60e 2017-10-03 Anton Zaytsev - Fixed. Add new CH_KERNEL_MAJOR to stm32 driver.
38702ff 2017-09-26 Pavel Kirienko - Merge pull request #112 from cvra/master
674133e 2017-09-25 Michael Spieler - Fix CAN driver for STM32F3 + ChibiOS