Simplify the package

This removes the need for AUTO_MKDIRS and bsd.prefs.mk. It also
leverages ${INSTALL_SCRIPT}, ${INSTALL_MAN_DIR}, ${INSTALL_MAN} and
${INSTALL_DATA} instead of just ${INSTALL}.

No change to PKGREVISION as the final binary should be identical.

With suggestions from leot@, thanks!

(khorben)