also compile the programs in the util directory by default, not only

do we want to test they can be compiled, but also samples may use/require
them. we might want to install them too, perhaps

util/zlib/Makefile

@@ -0,0 +1,17 @@
+
+.PHONY: mostlyclean clean
+
+zlib: warning
+#zlib: deflater
+
+warning:
+	@echo "deflater needs zlib installed, use 'make deflater' to build"
+
+deflater: deflater.c
+	$(CC) $(CFLAGS) -o deflater deflater.c -lz
+
+mostlyclean clean:
+	$(RM) deflater
+	
+install zip:
+