Made initial city styles to be derived from national styles. User selects national
style, not city style.

See patch #4589


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24700 a0f10bec-cc02-0410-94fc-a9cfff90b4cd
Fixed transforming terrain by mining or irrigation activities.

See bug #21805


git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@24701 a0f10bec-cc02-0410-94fc-a9cfff90b4cd