We already keep "Protocol 2" and "Protocol 4" opcodes separately, and
for a good reason - it must be clear for a person just by looking at
opcodes definition from which protocol version an opcode comes. However
at present Protocol 0 and Protocol 1 opcodes come all intermixed with
each other.

In the upcoming patches we'll be teaching Encoder to take desired pickle
protocol version into account (similarly to how pickle.dumps accepts desired
protocol version in Python), and then the encoder will have to use
different opcodes for different versions: for example if user asks to
produce "protocol 0" pickle stream it will be invalid to use "protocol
1" opcodes - e.g. BININT, EMPTY_TUPLE, etc.

So I went through

	https://github.com/python/cpython/blob/master/Lib/pickletools.py

for each opcode searching its protocol version and separated the opcodes
with proto=1 from protocol 0 opcodes.