CC3D - Fix builds that use l3gd20 - duplicate SPI code removed.
CC3D - Delete old SPI code.
Fix builds on targets that do not have sonar support.
STM32F3DISCOVERY - Fix build, MPU6000 not supported on this target yet.
CC3D - Support PPM input on IN_S1.

This required timer overflow events to be used in the calculation of PPM
channel data.

CC3D tested, other targets may be unstable as a result. Needs further
testing.