- Centralize the usage message.
- Document and enforce that -e and -m are mutually exclusive; previously, speficying both would result in only -e being applied.
- If -e was not specified, and -m was not specified or did not match, fall back to kldstat -n file which will always work for modules that aren't built into the kernel.
This means the kld and ntpd scripts can now rely on load_kld to dtrt.
MFC after: 1 week