opus

Include the doc dir in DIST_SUBDIRS instead of EXTRA_DIST

And explicitly specify what we want included in EXTRA_DIST of doc/Makefile.am,
otherwise make dist picks up whatever random junk you might have laying around
in that dir at the time you run it.

Tweak the top level delegation targets, because this means distclean will be
run in the doc dir by default now without our help.