The newest incarnation of http_filter. This is far from perfect, but it

The newest incarnation of http_filter.  This is far from perfect, but it
is a step in the right direction.  The idea is that the http_filter knows
about the http protocol.  So, it uses that knowledge to discover HTTP
request headers, and sends those headers up to getline.  However, it keeps
the request body saved in it's ctx pointer.

Later, when ap_get_client_block is called, we have set the remaining field
in the conn_rec.  This tells the http_filter how much of the remaining
data is request body, and how much isn't.  So, the http_filter can return
the request body unparsed up throught ap_get_client_block.

This doesn't even try to work with chunked input data, and there are still
some other bugs in it, but it works for small-ish files in my tests, and
it lets other people play with the concept of input filters.  I will try
to play with this more, but others should feel free to hack around in it
too.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86426 13f79535-47bb-0310-9956-ffa450edef68