Add a core_request_config so we have a safe semi-hidden place to save core data

Add a core_request_config so we have a safe semi-hidden place to save core data
that lives across function calls during a single request.  Change getline() to
take a request_rec parm (rather than a conn_rec) so we can access the
core_request_config.

This is in preparation for adding look-ahead functionality to getline(), so it
can support header line folding once again.  I'm committing these changes first
so the core_request_config can be used elsewhere (i.e. ap_get_client_block).

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86642 13f79535-47bb-0310-9956-ffa450edef68