kernel: Make sysvipc syscalls non-optional.

kernel: Make sysvipc syscalls non-optional.

Before this commit, we had three related kernel options, SYSVMSG,
SYSVSEM and SYSVSHM, to enable the syscalls. They were in all our
configs, but in theory the user could disable the functionality.
Having to deal with scenarios where they are not available is
unnecessarily complicated and there seems to be no real reason to
want to disable them.

For convenience, leave the three options as no-ops for now, so
adjusting the kernel config is not necessarily needed. We'll
change them to being unknown at some later point.

This commit also removes some parts which assumed that we had
sysvmsg.ko, sysvsem.ko and sysvshm.ko modules, like FreeBSD, but
this assumption was never true on DragonFly.