[boost] A grep like boost::iostreams filter.

Hi folks, I tried to use the regex_filter for grep like functionality, but I think it doesn't work like that. So, here goes a grep_filter and a driver main() function as an example. It is an input filter which returns only the matching lines of the given regex. I think it can be used by others, too. Is it possible to put this class into distribution, as an example maybe? Thanks, Emre Türkay