[XQuery] IBM-XQ-003: New term for in-scope namespaces

(IBM-XQ-003) At present, our documents are inconsistent in their use of 
the term "in-scope namespaces". In the XPath and XQuery documents, 
"in-scope namespaces" is part of the Static Context and is a property of 
an expression. On the other hand, in the Data Model and Functions and 
Operators documents, "in-scope namespaces" is a property of an element and 
has another meaning entirely. The term "in-scope namespaces" appears13 
times in the Data Model document and 10 times in F&O document. I think we 
should fix this inconsistency by changing the term "in-scope namespaces" 
in the Static Context to "declared namespaces" and using this term 
throughout the XQuery and XPath documents. The term "declared namespaces" 
suggests where the information comes from: either a namespace declaration 
in the Prolog, or a namespace declaration attribute. In this solution, no 
changes are needed to the Data Model and F&O documents.
--Don Chamberlin