xqxq: add collection support (at least 39 test cases)

[Sorin Marian Nasoi]

XQXQ has to provide ways for node collections support:
- adding a node collections to the list of available node collections in the Dynamic Context
- setting the default node collection

Please see:
- http://www.w3.org/TR/xpath-functions-30/#func-collection
- http://www.w3.org/TR/xpath-30/#id-xp-evaluation-context-components
- http://dev.w3.org/cvsweb/2011/QT3-test-suite/catalog-schema.xsd?rev=1.29;content-type=text%2Fplain
and look "collection"

The failures are part of the following test sets:
- prod-NamedFunctionRef: 14 failures
- fn-generate-id: 2 failures
- fn-function-lookup: 14 failures
- fn-collection: 9 failures

[Sorin Marian Nasoi (sorin.marian.nasoi)]

Assigned for redistribution and setting of 'Importance'.

[Dana Florescu (dflorescu)]

Sorin,

the handling of node collections is totally implementation defined. So W3C should not be allowed to test for this.

Please double check if this is correct (I am 95% sure), and file a bug against W3C.