xslt 1.6.11

This package has no dependencies.

### `xsl:attribute` content leaked into the caller's sequence

Reported by Martin Honnen against XSpec's `format-xspec-report.xsl`:

   XTTE0505: Template 'scenario-html-class-attribute' return value does not match
             declared type Attribute: expected exactly one item, got 2

His objection was the right one — a template whose body is a single `xsl:attribute` cannot
express two items, so the second had to come from the engine. It did: the attribute's VALUE was
landing in the caller's result sequence while the attribute node itself was built empty.

`xsl:attribute` has two branches. The one taken when `separator` is present isolates the
enclosing sequence; the common no-separator branch did not — and `xsl:sequence` checks for an
active sequence accumulator *before* any attribute-content check. So

   <xsl:attribute name="class">
     <xsl:choose>…<xsl:sequence select="'failed'"/>…</xsl:choose>
   </xsl:attribute>

inside a typed template appended `"failed"` to the caller. Verified against his actual
stylesheet: it now emits complete HTML with the correct `class` values.

### Both CLIs report the engines they bundle

`xquery --version` read 1.6.9 while embedding `PhoenixmlDb.Xslt` **1.6.6**, so four releases of
XSLT fixes were unreachable from the command line and nothing on screen said so. Martin had to
infer it from a repro that kept failing against a version that supposedly contained the fix.

   xslt 1.6.11 (PhoenixmlDb XSLT 3.0/4.0)
     PhoenixmlDb.Xslt 1.6.11
     PhoenixmlDb.XQuery 1.6.10
     PhoenixmlDb.Core 1.6.7

A version identifies the package, not what it carries. Printing it surfaced live drift on the
first run, which this release also clears (the XQuery pin moves 1.6.9 → 1.6.10).

### Package locations without another vendor's file format

`fn:transform` could only learn package locations from a Saxon configuration document, which
made another implementation's format a de facto dependency for `xsl:use-package`. There is now
a native vocabulary:

   'vendor-options': map {
       QName('http://phoenixml.dev/ns/vendor-options', 'packages'): map {
           'http://example.org/lib.xsl' : 'lib/library.xsl',
           'http://example.org/other'   : map { 'location': 'o.xsl', 'version': '2.0' }
       }
   }

Saxon's vocabulary is still read so existing stylesheets keep working, but it is now one
recognised vocabulary rather than the only door. Options in other vocabularies are ignored
rather than claimed — the first cut matched a bare local name `configuration` in any namespace,
which would have seized a foreign vendor's option and could mask a real one.

### Typed template bodies no longer double-count their own text

Text written inside a stylesheet function went to both the sequence accumulator and the output
buffer, and the pass that recombines them assumed they were disjoint — so a template declared
`as="text()"` returned two items with identical content. Two XSpec suites went from erroring at
the Run stage to completing.

   Xslt.Tests 1315 passed, 0 failed, 1 skipped (1310 at 1.6.10)
   XSLT conformance 10237/10630 = 96.30%
   XSpec: 62 of 284 suites complete end to end