SPI works (bit banging it).
Adding linking command for bcm library.
Adding support for SIGKILL signal.

	modified:   src/pip_sense_layer.cpp
Merge branch 'libusb1.0' (adding support for SIGKILL)
Fixing pip packet structure.

	modified:   src/pip_sense_layer.cpp
Data transfer is okay and faster, not decoding variable length packets.

	modified:   src/pip_sense_layer.cpp
Putting SPI into a different header and source file.
Working at a slow frequency.
Making SPI bus speed choice clear.

	modified:   src/spi.cpp
Merge branch 'master' into pi-spi

Master should not have had these changes in it.

Conflicts:
	src/pip_sense_layer.cpp

	modified:   src/CMakeLists.txt
	modified:   src/pip_sense_layer.cpp
	new file:   src/spi.cpp
	new file:   src/spi.h