MFC r290563,r290868,r291038:

r290563:

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

Also, fix eui64_aton_test:test_str(..). The test was comparing the result
of eui64_aton to a pointer of the expected result.

Sponsored by: EMC / Isilon Storage Division

r290868:

Fix -Wformat issues

Reported by: gcc
Sponsored by: EMC / Isilon Storage Division

r291038:

Do not print out errno if the call succeeded unexpectedly; this was a mistake
made in r290868

Reported by: jilles
Sponsored by: EMC / Isilon Storage Division