Deprecate Saxon 9.7 or less

[AirQuick]

Saxon 9.7 or less should be deprecated explicitly:

• In Release Note
• In Wiki (probably Installation)
• In run time message?

Rationale:

• Burden on development and testing, both on XSLT and XQuery, primarily because of limited support of XPath/XSLT/XQuery 3.x, partially because of differences in command interface
• No longer maintained by Saxonica

[AirQuick]

@xspec/xspec
I'd like to propose

• Create a Wiki page, titled Requirements, under Installation section.
• Move Requirements blocks from Installation on Mac and Linux and Installation on Windows to the new Requirements page.
• Add these warnings to the new Requirements page.
  • Saxon 9.7 (or less) is deprecated. XSpec is not tested regularly on 9.7.
  • For the moment, XSpec will be tested only occasionally on 9.7. (*1)
  • At some point in the near future, XSpec will stop being tested at all on 9.7 and probably will stop functioning on 9.7 HE (*2)

[1] I'm testing XSpec occasionally on 9.7 for some practical reasons. So I'll continue it for the moment.
[2] "All XSLT 3.0 features require at least Saxon-PE."

[cirulls]

@AirQuick: this sounds good to me, the deprecation warning will be very useful for helping people migrating to the latest Saxon.

[AirQuick]

• Create a Wiki page, titled Requirements, under Installation section.
• Move Requirements blocks from Installation on Mac and Linux and Installation on Windows to the new Requirements page.

Done.

[AirQuick]

• Add these warnings to the new Requirements page.

Done.
Reflecting our CI configuration, I also added a statement, "XSpec is tested on Java 8."

[AirQuick]

• In run time message?

Done in #625. Thanks for the review, @cirulls and @galtm.

[cirulls]

I think the move to Java 8 for testing XSpec and the deprecation message for Saxon 9.7 could be mentioned explicitly in the highlights for the next release notes so that users are aware of it.

[AirQuick]

I think the move to Java 8 for testing XSpec and the deprecation message for Saxon 9.7 could be mentioned explicitly in the highlights for the next release notes so that users are aware of it.

How we communicate it, I'll leave it up to you.
Ironically, for the first time, we have continuous testing on Saxon 9.7 :)