shadow: rely on propagated findXMLCatalogs hook

shadow uses a copy of m4 from gtk-doc so we need to apply the same
fix as in 407db7b019.

Also patch it to use the correct DocBook version.

pkgs/os-specific/linux/shadow/respect-xml-catalog-files-var.patch

@@ -0,0 +1,30 @@
+diff --git a/acinclude.m4 b/acinclude.m4
+index dd01f165..e23160ee 100644
+--- a/acinclude.m4
++++ b/acinclude.m4
+@@ -46,9 +46,21 @@ AC_DEFUN([JH_CHECK_XML_CATALOG],
+     ifelse([$3],,,[$3
+ ])dnl
+   else
+-    AC_MSG_RESULT([not found])
+-    ifelse([$4],,
+-       [AC_MSG_ERROR([could not find ifelse([$2],,[$1],[$2]) in XML catalog])],
+-       [$4])
++    jh_check_xml_catalog_saved_ifs="$IFS"
++    IFS=' '
++    for f in $XML_CATALOG_FILES; do
++      if [[ -f "$f" ]] && \
++        AC_RUN_LOG([$XMLCATALOG --noout "$f" "$1" >&2]); then
++        jh_found_xmlcatalog=true
++        AC_MSG_RESULT([found])
++        ifelse([$3],,,[$3])
++        break
++      fi
++    done
++    IFS="$jh_check_xml_catalog_saved_ifs"
++    if ! $jh_found_xmlcatalog; then
++      AC_MSG_RESULT([not found])
++      ifelse([$4],,[AC_MSG_ERROR([could not find ifelse([$2],,[$1],[$2]) in XML catalog])],[$4])
++    fi
+   fi
+ ])