Proposed changes to terrain alteration in civ2civ3 ruleset.

[kevin551]

I know the game is about to start - but it seems to have been delayed slightly.
The test game has kept going for a while and we have got to play with geo-engineers.
There is one terrain transformation that is now impossible.
You cannot transform most land to ocean.
The example on our map is that I cannot cut the landbridge by digging a canal across it.
From Jungle -> Swamp -> Ocean is possible, but you cannot make Jungle.

In the default ruleset forest could be mined to swamp, this has been removed.
I would like to bring back this action.

It also works if irrigating forest makes jungle and then mining forest makes plains.