Freeciv

While the change is simple, it requires a lot of work to do those simple changes everywhere. Thus:

1) Retarget to S3_3. It's enough to do this for one branch, without going through the pain of backporting to older branch
2) Instead of one big patch, go through migration period where both old and new name are accepted

Attached patch begins such a migration period. Supplied rulesets are not changed, but still use the old name.

- Fix existing 3.2 -> 3.3 conversions that add User Unit Type Flags.

- Rebased