l10n: vi.po: Update Vietnamese translation

Signed-off-by: Trần Ngọc Quân <vnwildman@gmail.com>
xzgrep: Avoid passing both -q and -l to grep.

The behavior of grep -ql varies:
  - GNU grep behaves like grep -q.
  - OpenBSD grep behaves like grep -l.

POSIX doesn't make it 100 % clear what behavior is expected.
Anyway, using both -q and -l at the same time makes no sense
so both options simply should never be used at the same time.

Thanks to Christian Weisgerber.
Add support for AmigaOS/AROS to tuklib_physmem().

Thanks to Fredrik Wikstrom.
Update THANKS.