editors/micro: Add (experimental) AUTOCOMPLETE option

[koobs]

Summary

editors/micro: Add (experimental) AUTOCOMPLETE option

Pull upstream PR #977 [1] into a patch to provide autocomplete
functionality to the micro editor to facilitate testing, bug reports and
feature requests.

Put it behind a non-default AUTOCOMPLETE option as it is experimental for
now, though it appears well-tested.

It currently provides Go language autocompletion and a prototype generic
autocompletion mechanism for tokens currently in the document

While I'm here, pet portlint (DISTVERSIONPREFIX appears out-of-order)

[1] https://github.com/zyedidia/micro/pull/977

Submitted by: skered (via IRC) [1]
Reviewed_by: swills (maintainer)
Approved by: swills (maintainer)
Differential_Revision: D20817

Test Plan

portlint: OK (looks fine.)
testport: OK (poudriere: 12amd64)

[koobs]

Upstream PR closed in favour of chasing LSP support:

https://github.com/zyedidia/micro/issues/1138
https://github.com/AndCake/micro-plugin-lsp