clean stale, unused branches

[zhaozg]

There are a lots of branch to fix issues or try new features, but they too old, and I think it is unused anymore.

I have remove some merged branches, and others I can't make up mind.

So, we need do somethings, branch owners please delete them if unused, or do discuss for that.

branch	safe to delete	vote
coro-error
error-redo
fix-luvi
lightuserdata
schema

schema need talk about.

zhaozg +1 for deletable branchs.

Keep listening voice from @luvit/luvit-admin and contributors.

@Bilal2453 give options, and I narrow it. delete uv-update-1.0.0,upstream-cwd-fix, luvi-build are safe, see comment

[Bilal2453]

All current branches are safe for deletion as they have been merged except for 6: lightuserdata, coro-error, uv-update-1.0.0, upstream-cwd-fix, luvi-build, fix-luvi. If that helps.

note: I looked at fix-luvi, which updates luajit and libuv to a currently outdated version, removes lua-compat-5.3, and manually does Lua 5.2/5.3 compatibility checks (for a couple of things). Doesn't seem applicable in current luvi/luv.

[zhaozg]

uv-update-1.0.0 should be delete, now we already libuv v1.x.
upstream-cwd-fix should be delete, which already solved on 2014-10-17, upstream libuv bug.
luvi-build should be delete, which already merged on 2018-04-24 by Tim Caswell.