CD-1 issue #49: identifier of dayTimeDuration

The issue number refers to the XLS-sheet found in this email:
http://lists.oasis-open.org/archives/xacml/200909/msg00013.html

The commenter notes that there are still places in the text where an 
XACML specific dayTimeDuration data type identifier is used in place of 
the official W3C identifier.

I propose that we fix this and use the W3C identifier consistently.

Best regards,
Erik