• Fix async write issue that sometimes led to selection of wrong timeout
  vs. keepalive timeout selection for idle sessions.
• Checking LimitRequestLine, LimitRequestFields and
  LimitRequestFieldSize configurated values for incoming streams. Returning
  HTTP status 431 for too long/many headers fields and 414 for a too long
  pseudo header.
• Tracking conn_rec->current_thread on slave connections, so
  that mod_lua finds the correct one. Fixes PR 59542.
• c->aborted also set for slave connections when main connection is closed by client