engine: reference to alias in WHERE clause doesn't work

[tpdenk]

Describe the bug
When referencing a column alias in a WHERE clause, the respective column can't be found.

To Reproduce
See TestExample07 and remove t.Skip(), then run it.

Expected behavior
No error.

Additional context
This might be a compiler issue, however, not sure if we should invert selection and projection just to make this happen. We should first check whether the column information is available in the where clause, and if so, make use of it and resolve the correct column.