Accept x:description without XSpec namespace prefix

[AirQuick]

Closes #572

This pull request

• sets a fallback prefix (XsPeC:) when the test author does not provide a prefix to the XSpec namespace (http://www.jenitennison.com/xslt/xspec) in x:description.
• also modifies a namespace declaration on XQuery so that it works without a prefix.

Tests

As far as I know, most test authors provide a prefix (x: in most cases) to the XSpec namespace. SchXslt is the only use case I've ever found. So I didn't write the test for this pull request extensively.

• xspec-no-prefix.xspec tests both XQuery and XSLT.
• For Schematron (xspec-no-prefix_schematron.xspec) and XSLT-only (xspec-no-prefix_stylesheet.xspec), I just copied some of the existing test files and removed the x: prefix.

Note for the test result

I found weird behaviors in xspec-no-prefix_stylesheet.xspec with some Saxon versions:

9.7.0.21-EE

• The tests are reported as Failure. (not expected)
• The report XML (created as test/xspec/xspec-no-prefix_stylesheet-result.xml) omits xmlns="" from elements in x:result and x:expect. (not expected)

9.7.0.21-HE, 9.8.0.12-EE/HE, 9.8.0.14-EE/HE

• The tests are reported as Success. (as expected)
• The report XML omits xmlns="" from elements in x:result and x:expect. (not expected)

9.8.0.15-EE/HE, 9.9.1.4-EE/HE

• The tests are reported as Success. (as expected)
• The report XML has xmlns="". (as expected)

Because the latest Saxon versions are working as expected, I haven't investigated the problem further.
Probably it's related to Saxon bug 3889 which was fixed on 9.9.0.1 and 9.8.0.15.

[galtm]

@AirQuick : I should have a code review by Monday. (Will be away from computers tomorrow, FYI.)

[galtm]

The changes look fine.

[AirQuick]

@cirulls
Merged this enhancement.

Thanks @galtm for the review.