- Added code to take care of the situation where while processing the first

- Added code to take care of the situation where while processing the first
  server response (which includes the server header), after finding the end
  of the headers we were not looking past the end of the headers for
  content modification. I enabled it for filter_popups.
  Someone else should look to see if other similar operations should be
  done to the discarded portion of the buffer.