*) Clarified the specific MIME information (MimeType key) that would
warrant the inclusion of sysutils/desktop-file-utils/desktopdb.mk, as there
are other MIME-related keys that appear in *.desktop files.

*) Synthesize recent discussion about DIST_SUBDIR on pkgsrc-bugs@ into the
guide, as this is important, no one did it, and I have time to do it now.
Break that very large paragraph into four smaller, sensible ones.

(rodent)