#129 xsl:attribute name="xmlns:x" isnt an error

[Michael Kay]

The XSLT 1.0 specification is quite explicit that it is
not an error to write

<xsl:attribute name="xmlns:thing"
namespace="whatever">...</xsl:attribute>

Saxon however reports this as a recoverable error. It
recovers by ignoring the attribute; the correct action
is simply to ignore the prefix "xmlns".

Applies to Saxon 6.5.2, 7.4, and all other releases.

Test case: atrs23

Source code fixed in both branches.