Network protocol: Send each effect rule in a single packet.

Thanks to the work of Emmet Hikory <persia> effects now use a single requirement
vector. This makes it easy to simplify the network protocol.

See patch #4886

git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@25374 a0f10bec-cc02-0410-94fc-a9cfff90b4cd