Upgrade to libxml 2.9.2 and libxslt 1.1.28

third_party/libxslt/xslt-config.in

 #! /bin/sh
 
 prefix=@prefix@
 exec_prefix=@exec_prefix@
 exec_prefix_set=no
 includedir=@includedir@
 libdir=@libdir@
 
 usage()
 {
@@ skipping 71 matching lines @@
         ;;
 
     *)
         usage
         exit 1
         ;;
     esac
     shift
 done
 
-the_libs="@XSLT_LIBDIR@ @XSLT_LIBS@"
+the_libs="@XSLT_LIBDIR@ @XSLT_LIBS@ @EXTRA_LIBS@"
 if test "$includedir" != "/usr/include"; then
     the_flags="$the_flags -I$includedir `@XML_CONFIG@ --cflags`"
 else
     the_flags="$the_flags `@XML_CONFIG@ --cflags`"
 fi
 
 if $cflags; then
     all_flags="$the_flags"
 fi
 
@@ skipping 25 matching lines @@
 for i in $rev_libs; do
     case " $ord_libs " in
     *\ $i\ *) ;;                        # already there
     *) ord_libs="$i $ord_libs" ;;       # add it to output in reverse order
     esac
 done
 
 echo $other_flags $ord_libs
 
 exit 0