Produce ctwill.pdf with XeTeX.

MuPDF on Android 7.1 has massive problems displaying 'ctwill.pdf'
created by pdfTeX.  The dual-step process with XeTeX and xdvipdfmx
produces a better result.  It suffices to do this in the final loop.

Author: ascherer

makeall

@@ -217,7 +217,7 @@ FI
 	if [ ctwill = $f ]
 	then
 		ctwill-refsort < $f.ref > $f.sref
-		$TEX $f
+		xetex $f
 	fi
 done