Add support for positional-only parameters in Python#4

Open

serhiy-storchaka wants to merge 2 commits intomasterfrom posonly-dunders

+1,828-2,171

Commits on Apr 2, 2019

AC: Use a double underscore for positional-only parameters.
serhiy-storchaka
committed
Forbid to pass argument by name if it starts with '__'.
serhiy-storchaka
committed