Introduce startup scripts from the local_startup directories to
the base rcorder. This is accomplished by running rcorder twice,
first to get all the disks mounted (through mountcritremote),
then again to include the local_startup directories.

This dramatically changes the behavior of rc.d/localpkg, as
all "local" scripts that have the new rc.d semantics are now
run in the base rcorder, so only scripts that have not been
converted yet will run in rc.d/localpkg.

Make a similar change in rc.shutdown, and add some functions in
rc.subr to support these changes.

Bump __FreeBSD_version to reflect this change.