Fix page issue in subqueries caused by copy without copying page param

I've found a bug in Squeryl:

val f = from(table1)(t => select t).page(5, 5)
join(f, table2)((t1, t2.left) => ... on (f.t2Id === t2.id)...

The idea is to limit subquery and then join another table. Now Squeryl does not limit subquery due to wrong copy function. This commit fixes this bug.