Rework Makefiles one more time.

- use printf to print commands rather than echo, which it may not have
  support for escape sequences (-e).
- Remove DESTDIR from SBINDIR, MANDIR, LIBDIR and INCLUDEDIR so that
  you can override it.

--HG--
extra : convert_revision : xtraeme%40gmail.com-20100124125958-8mscedj5ntf288jd

include/Makefile

@@ -7,12 +7,12 @@ all:
 
 .PHONY: install
 install:
-	install -d $(INCLUDEDIR)
-	install -m 644 $(INCS) $(INCLUDEDIR)
+	install -d $(DESTDIR)$(INCLUDEDIR)
+	install -m 644 $(INCS) $(DESTDIR)$(INCLUDEDIR)
 
 .PHONY: uninstall
 uninstall:
-	-rm -f $(INCLUDEDIR)/$(INCS)
+	-rm -f $(DESTDIR)$(INCLUDEDIR)/$(INCS)
 
 .PHONY: clean
 clean: