MFC r223148, r240252, r241541, r241543, r245756:

MFC r223148, r240252, r241541, r241543, r245756:

r223148: (ru)
 - Document all trees that support CVS_UPDATE.
 - Document all trees that support SUP_UPDATE.
 - Document SVN_UPDATE.
 - Document NO_WWWUPDATE.
 - make.conf(5) mistakenly said that *SUPFILE* had defaults.
 - Add an example entry for WWWSUPFILE.

r240252: (eadler)
 - Remove documentation and www cvsup files as they are no longer
   useful with the switch to subversion.

r241541: (joel)
 - Minor mdoc improvements. Also remove unnecessary csup reference.

r241543: (eadler)
 - Bump .Dd

r245756:
 - Mark SUP_UPDATE as deprecated in make.conf(5), providing
   instructions to use SVN_UPDATE or freebsd-update(8).
 - While here, remove bogus NO_WWWUPDATE.

git-svn-id: svn://svn.freebsd.org/base/stable/8@245864 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f