Update ChibiOS submodule.

Latest commit in the tegesoft fork has build binary option.
Require Python 2.7 and Python 3.2.

Require Python 2.7 for building protobuf sources. FindNanopb.cmake
hardcodes a call to 'python' which is set to python2 on many systems
and protobuf is not supported in Python 3.
This partially reverts 6002d51d32418dc67c2ef0ecb34d4f0390544cb5.
Fix python command in FindNanopb.cmake.

Modify FindNanopb.cmake to use PYTHON_EXECUTABLE found by CMake instead
of hardcoding 'python' command.