Remove $FreeBSD$: two-line .h pattern

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

libc/nss tests: Style

Sponsored by: The FreeBSD Foundation
MFC after: 1 month

Read the contents of the snapshot files properly

- Use fgetln instead of fgets; localize complexity related to fgetln(3)
inside the loop.
- Skip over blank lines.
- Skip over lines (properly) that start with a "#"

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division

Integrate tools/regression/lib/libc/nss into the FreeBSD test suite as
lib/libc/tests/nss

- Convert the testcases to ATF
- Do some style(9) cleanups:
-- Sort headers
-- Apply indentation fixes
-- Remove superfluous parentheses
- Explicitly print out debug printfs for use with `kyua {debug,report}`; for
items that were overly noisy, they've been put behind #ifdef DEBUG
conditionals
- Fix some format strings

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division