rc.d: Clean up and tweak dependencies - Don't use real entries in the dummy scripts; instead, use the dummy entries in the real rc scripts. This makes the dummy entries clean. - Use dummy entries instead of one/multiple real entries (such as 'root') wherever appropriate. - Use 'REQUIRE' instead of 'BEFORE' wherever appropriate, which makes it clearer to understand. - Simplify and clean up various dependencies; remove unnecessary requires. - Tweak dependencies of some scripts to make the startup order more sensible. For example, make 'hostname' and 'ip6addrctl' run a bit later, after 'FILESYSTEMS' but before 'NETWORKING'. Referred to FreeBSD for some changes.