(failing) test for proposed change to when _distinct and _fieldset used together:

my @distinct_authors = Models::Book -> get_many( _distinct => 'yes',
						 _fieldset => [ 'author' ] );

Should mean " select distinct author from books ".
Can now specify on which column to distinct:

Models::Book -> get_many( _distinct => [ 'author' ],
			  _fieldset => [ 'author' ] );

or:

	my $afield = Models::Book -> borrow_field( 'author' );

	my @distinct_authors = Models::Book -> get_many( _distinct => [ $afield ],
							 _fieldset => [ $afield ] );

.