MDEV-22689 MSAN use-of-uninitialized-value in decode_bytes()

This was not a user visible issue as the huffman code lookup tables would
automatically ignore any of the unitialized bits

Fixed by adding a end-zero byte to the bit-stream buffer.

Other things:
- Fixed a (for this case) wrong assert in strmov() for myisamchk
  and aria_chk by removing the strmov()