Some required changes for CLSQL to work under Lispworks 7.

[tdrhq]

I've been using this for a while now. LW7 requires an extra option to make sure slot values are not optimized when using MOP.

The second fix is minor, I don't remember how exactly it affects CLSQL. But the feature check +:lispworks6 was used, whereas we really need something like lispworks6+. Since that feature doesn't exist we follow LW's guidelines and check for whether it's not lispworks4 or 5.