setSelect was calling deprecated addselect

When I call SQLQuery->setSelect() I get a user deprecated error:

`[User Deprecated] SQLQuery->addSelect is deprecated. Use selectField() to specify column aliases. Called from SQLQuery->setSelect.`

As far as I know, setSelect isn't deprecated (it'd be a pain to use selectField() multiple times rather than just passing an array of select clauses). The problem is that setSelect itself calls the deprecated addSelect function.

So I guess setSelect should do something like below, where it recreates the behaviour of addSelect without actually calling it and minus the deprecation error.