Log Message:
pkgsrc/doc/guide: Restate MAINTAINER/OWNER protocol

Acting for PMC, restate the guidelines for MAINTAINER and OWNER.  This
is intended to capture what we think has been viewed by us and others
as good practice, even though some of it was not manifest in the text
before.  Compared to before:

  Strengthen the notion that MAINTAINER should be consulted for more
  than micro updates.  The old text, for whatever reason, didn't say
  that.  Document the reciprocal obligation that MAINTAINER should
  respond reasonably promptly.

  State that OWNER is used in relatively rare circumstances.  Document
  reciprocal obligations for OWNER that are much stronger than
  MAINTAINER's reciprocal obligations.