The output of generate-id(), when applied to an
attribute or namespace node, may contain characters
that are not alphanumeric and/or are not ASCII characters.
This is a non-conformance with the spec which is
present in 7.6.5 and all previous releases. It is also
present in 6.5.3.
Reported by Anton Lapounov [email@example.com]
Test case added: expr90
Source code fixed.