register a list of other packages with which they conflict (via the
-C option to pkg_create), and they will refuse to install (unless -f is
specified) if one of the listed packages is already present.
* Update documentation for the new feature as well as fleshing out some
existing documentation.
* Bump PKG_INSTALL_VERSION so this feature can be tested for.
Submitted by: Sergey Matveychuk <sem@ciam.ru>
PR: bin/47145
MFC after: 2 weeks