XSD issue #118: SearchQueryType open content.

[Gary P Cole <Gary.P.Cole@Sun.COM>]

At least one reviewer was confused by the lack of any indication in the 
XSD that SearchQueryType could contain a <select> element.

The spec explains (in section 3.3.4 SearchQueryType) that open content 
of SearchQueryType is one or more instances of QueryClauseType 
(including SelectionType) or LogicalOperator.

This deserves annotation in the XSD because specified behavior relies on 
open content
(similar to the nesting of requests within a batchRequest). 
The spec snippet in section 3.3.4 contains a suggested annotation in 
bold font.