Remove $FreeBSD$: two-line .h pattern

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

Add the start of libc and libstand for arm64. Not all of the machine
dependent functions have been implemented, but this is enough for world.

Differential Revision: https://reviews.freebsd.org/D2132
Reviewed by: emaste
Sponsored by: The FreeBSD Foundation