Support run in stream subsystem

[tzssangglass]

Hi folks, thank you for open sourcing this lib.

Since the ngx.semaphore API already support for ngx_stream_lua(ref: openresty/lua-resty-core@4e5a130), will you consider supporting running this lib in the stream subsystem?

I do some test and hacked supported_semaphore_wait_phases like:

  local supported_semaphore_wait_phases = {
    rewrite = true,
    access = true,
    content = true,
    timer = true,
    ssl_cert = true,
    ssl_session_fetch = true,
    preread = true,
  }

it works well in stream subsystem.