sk(4)) were reversed.
While I'm here, update list of cards supported by sk(4) to be consistent
with the manpage.
PR: docs/21700
Submitted by: neuf@lrs.e-technik.uni-erlangen.de
o Define a RELN_ROOT variable which points to the root of the relnotes
tree (i.e., src/release/doc).
o By default, define DOC_PREFIX in terms of RELN_ROOT; this gives a
bigger chance of finding the doc/ tree without help in the form of
setting DOC_PREFIX on the command line.
o Respect DOCDIR; `make install` works now.
Approved by: bmah
