send "startup" message 5 minutes after startup, not immediately

Makefile.am:
  mariadb uses .la libraries for static plugins.
  mysql - .a libraries
plug.in:
  mariadb uses .la libraries for static plugins.
  mysql - .a libraries
sender_thread.cc:
  send "startup" message 5 minutes after startup, not immediately
url_http.cc:
  avoid "unused variable https" warning