stream.jl: provide flush() for all AsyncStream types (e.g. Pipes, TTYs, and TCP/UDP sockets)
fix #4376
Merge pull request #4329 from nlhepler/lh/flush

stream.jl: provide flush() for all AsyncStream types (e.g. Pipes, TTYs, ...
Merge branch 'master' of https://github.com/JuliaLang/julia