- Remove obsolete checks
- Fix checks that are inconsistent
- Stop compiling compare256/longest_match variants that never gets called
- Improve how the generic compare256 functions are handled.
- Allow overriding OPTIMAL_CMP
This simplifies the code and avoids having a lot of code in the compiled library than can never get executed.
This was missed in #1831. The RLE methods compare a string of bytes
directly with itself to directly derive a simple run length encoding.
They use similar but not identical methods to compare256. This needs
a similar endianness check at compile time to know which compare bit
count to use (leading or trailing).
