Fixes:

• Correct conversion from uint24 to other ints (#39, @rixed)
• Fix conversion from all ints to uint24 and int24 (#41, @rixed)
• Fix int24 failing to recover from casts (#43, @rixed)
• Fix sign extensions (#49, @rixed)
• Long_val returns intnat, previously long was used (#53, @dra27)
• Reduce size of marshalled custom values on 4.08+ (#54, @dra27)
• Store 128-bit ints as structs to prevent unaligned access (#55, @dra27)

New features:

• Add of_substring (#49, @darlentar)

0.6.0 (12/3/2019)

• Speed up generic comparison of int backed types (#34, @rixed)
• Port to dune (#35, @tuncer)
• Move to stdlib from pervasives (#36, @tuncer)