Consistency fix for disloged girders securing and building on

Made building on/securing disloged girders consistent with secured girders, by preventing disloged girders from being secured or build on if on a forbidden turf (space, shuttle, ...).

After all, if the floor (or lack of) prevent building a girder, bringing an unsecure disloged one is not going to make it any better.

Fixes #4436 (at least partially)