Validate BitScrambler program headers against the supported format and
hardware limits before using header-derived instruction and LUT sizes.
Also add regression coverage for malformed headers and document that the
program blob must come from a trusted assembler output.
Reject LUT loads that exceed the hardware address space and assemble
each 32-bit LUT word via memcpy so unaligned and partial inputs do not
read past the caller buffer. Add regression tests for oversized and
partial unaligned LUT loads.
This adds an assembler for the BitScrambler assembly language,
plus unit tests for it. It also adds the loopback driver,
which can do BitScrambler operations on memory-to-memory
transfers. Documentation is also included.
