Fix problem with in ($coloumns) of

Running a filter `in city of London` was returning an SQL error saying `t1_1.city`
is not defined. This should fix the problem by adding the join statement at the end
similar to what is done to the `within` statement.

I also took the freedom to edit another two lines. Looking at the code you could probably externalize $field_id and probably the $joins statement if made coherent with the other-one but I did not want to change your code structure & table names.