ArgumentDo proposal updated

[Akio Takano]

Hi glasgow-haskell-users,

Thank you for all the feedback to the ArgumentDo proposal. Following
the discussion, I made changes to the proposal and updated the wiki
page [0].

Now the proposed grammar is greatly simplified: it doesn't add a new
non-terminal anymore, indeed it removes one instead. The proposed set
of accepted programs remains unchanged.

I hope the this update addresses one major concern that was raised in
the previous discussion.

Any feedback is appreciated.

Regards,
Takano Akio

[0]: https://ghc.haskell.org/trac/ghc/wiki/ArgumentDo