[boost] Iostreams 'drain' algorithm proposal

Hello list. New here, but a Boost user so thought it was time I started lurking with a view to contributing. When using boost::iostreams, I find I frequently need/implement a 'drain' algorithm. This is identical to boost::iostreams::copy, except that it doesn't close the Sink. This allows mutiple sources to be 'drained' into a single sink. Unless there is a generic algorithm for doing this that I have missed, I'd like to propose the addition of the 'drain' algorithm to boost::iostreams. I have a patch, should there be any interest. Andrew Walrond