Bring back link-mso19/nexus-osciprime for now.

This patch will be re-introduced later.
README: Add "Copyright and license" section.
fs9922: Use common DMM API.

Use the same functions and structs as the other DMM protocol parsers
in hardware/common/dmm. Among other things, this allows the functions
to be used from drivers in a generic way, e.g. in serial-dmm, uni-t-dmm,
and possibly other drivers.
common/dmm: Drop obsolete *is_packet_start() functions.
uni-t-dmm: Make driver more similar to serial-dmm.
uni-t-dmm: Do proper detection of packets in the stream.

Also, various fixups in the driver.
Remove sr_rational
gnuplot: fix for big-endian architectures.
vcd output: fix for big-endian architectures.