resultSet.relative() behavior is incorrect when crossing result set boundaries

When going forward (positive offset), reaching the position just after the last row will make relative() return true (as if the result set was positioned on a row).

When going backward (negative offset), trying to reach a row before the first will never work: the result set will appear "stuck" on the first row.

According to the ResultSet interface's Javadoc (java.sql.ResultSet#relative):

Attempting to move beyond the first/last row in the
result set positions the cursor before/after the
the first/last row.

And:

@return <code>true</code> if the cursor is on a row; <code>false</code> otherwise

So the current behavior is incorrect.

PR with test cases (and hopefully a fix) coming soon.