Change directory build order. png needs to come before pngcom. This is...

Change directory build order. png needs to come before pngcom. This is finishing up pnunn last checkin.... Added png and zlib library link. pnunn. refer to Bug#5459. review:slamm. ok'd:chofmann.

modules/libimg/Makefile.in

@@ -22,12 +22,12 @@ VPATH		= @srcdir@
 
 include $(DEPTH)/config/autoconf.mk
 
-DIRS = public public_com src gifcom pngcom jpgcom
-
 ifndef MOZ_NATIVE_PNG
-DIRS += png
+DIRS = png
 endif
 
+DIRS += public public_com src gifcom pngcom jpgcom
+
 EXTRA_LIBS = $(PNG_LIBS) $(ZLIB_LIBS)
 
 include $(topsrcdir)/config/rules.mk