[libpng16] Checked in new Makefile.am that maintains pngusr.dfa

Makefile.am

@@ -184,11 +184,11 @@ endif
 	mv $*.tf3 $@
 
 # The .dfn file for pnglibconf.h is machine generated
-pnglibconf.dfn: scripts/pnglibconf.dfa scripts/options.awk pngconf.h $(DFA_XTRA)
+pnglibconf.dfn: scripts/pnglibconf.dfa scripts/options.awk pngconf.h pnguser.dfa$(DFA_XTRA)
 	rm -f $@ $*.tf[45]
 	$(AWK) -f ${srcdir}/scripts/options.awk out=$*.tf4 version=search\
 	    ${srcdir}/pngconf.h ${srcdir}/scripts/pnglibconf.dfa\
-	    $(DFA_XTRA) 1>&2
+ 	    ${srcdir}/pngusr.dfa $(DFA_XTRA) 1>&2
 	$(AWK) -f ${srcdir}/scripts/options.awk out=$*.tf5 $*.tf4 1>&2
 	rm $*.tf4
 	mv $*.tf5 $@