libxslt: Fix of 6 CVEs

CVE-2019-11068: fix security framework bypass in xsltCheckRead and xsltCheckWrite callers - CVE-2019-18197: fix dangling pointer in xsltCopyText - CVE-2019-5815: always set context node before calling XPath iterators - CVE-2021-30560: fix use-after-free in xsltApplyTemplates - CVE-2024-55549: fix...