Change ap_get_brigade prototype to remove *readbytes in favor of readbytes.

If you need the length, you should be using apr_brigade_length.  This is
much more consistent.  Of all the places that call ap_get_brigade, only
one (ap_http_filter) needs the length.  This makes it now possible to
pass constants down without assigning them to a temporary variable first.

Also:
- Change proxy_ftp to use EXHAUSTIVE mode (didn't catch its -1 before)
- Fix buglet in mod_ssl that would cause it to return too much data in
  some circumstances


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93014 13f79535-47bb-0310-9956-ffa450edef68