Take another shot at reimplementing core_output_filter. This implementation buffers

brigades across multiple calls until MAX_IOVEC_TO_WRITE or
MIN_SIZE_TO_WRITE thresholds are hit. This implementation does not attempt
to coalesce bytes. Moving a bit further down the filter learning curve...


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86389 13f79535-47bb-0310-9956-ffa450edef68