[xacml-comment] Conventional XML namespace prefixes

[Satoshi Hada <SATOSHIH@jp.ibm.com>]

Section 1.2 summarizes the conventional XML namespace prefixes.
The two prefixes "xacml" and "xacml-context" should be added to the
convention.

These two prefixes are used many times, but it seems to me no definition is
given in the specification document.
Of course, they are defined in the (complete) schema files.
However, it's better to add them to Section 1.2 for readability.

Also, xmlns:xacml=... can be removed from the request context example in
Section 4.2.2 because
the "xacml" prefix is not used in it.

Satoshi Hada
IBM Tokyo Research Laboratory
mailto:satoshih@jp.ibm.com