release-3.9.1: Get ready for release 3.9.1

• Go over list of available Python versions
• 3.8.0alpha3 tolerance

release-3.9.0

Correct instruction field inst_size in instructions that were build from EXTENDED_OP instructions.

Add has_extended_arg field in instruction.

release-3.8.10

• 3.8 opcode support
• Add Python 2.7.16