Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

other: Fix several typos and minor errors

- duplicate words
- typos
- references to old versions of FreeBSD

Reviewed by: imp, benno

Integrate tools/regression/fifo into the FreeBSD test suite as tests/sys/fifo
and tools/regression/file into the FreeBSD test suite as tests/sys/file

MFC after: 1 week