Update usr/Makefile
Update usr/Makefile

 - This improves the user messages.

 - This update the pkgsrc checkout rules to point to the new repository,
   as well as the new work process we are introducing.

 - This introduces rules for the MINIX sources, as we don't have the
   space anymore to distribute them by default on the official ISO.

Change-Id: Id1867286bd15efc46bad1d906c1ca1b3a883b064

veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi