* Low impact changes from path_cleanup branch.
This is a step towards minimizing the diff with path_cleanup branch.
* Update ecl.
* Revert matrix update.
* Revert ecl and matrix.
* Update sitl gazebo.
* Revert sitl_gazebo and matrix changes.
The reason for this change is that RPi2 and RPi3 are compatible, and
hopefully all differences coming up can be resolved without ifdefs but
at runtime.