[WIP/RFC] Add some more IO locks to printing

[iamed2]

Right now you can get mixed output with async code:

function foo(n)
    @sync begin
        @async (sleep(0.05); printstyled(stdout, ntuple(_ -> "foo", n)...; color=:blue))
        @async print(stdout, ntuple(_ -> "bar", n)...)
    end
end

julia> foo(30)
barfoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoobarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarTask (done) @0x0000000117d2d690

In this case printstyled is actually doing a single print under the hood, after writing the string to a buffer. While there is a lock in vararg print, there was no lock in single-string print. This means that the foo string could be shoved right in the middle of the bars as it was ignoring the lock that vararg print had.

AFAICT this just means we need more locks. I have added some locks. If people agree, I will add all the locks.

I also think that lock(f, x::AbstrackLock) should probably be expanded to lock(f, x::Any).

[omus]

I'm in favour of this