Separate plugin_send from the send implementation
Separate plugin_send from the send implementation

The public-facing API will eventually communicate cross-thread instead
of writing directly to the brigade. In preparation, pull the send logic
into an internal function, and call that from the read loop instead of
mod_websocket_plugin_send.

jchampio/apache-websocket,jchampio/apache-websocket,jchampio/apache-websocket