xfsprogs: Removing deprecated _BSD_SOURCE definition.

xfsprogs: Removing deprecated _BSD_SOURCE definition.

In glibc 2.20, _BSD_SOURCE was deprecated in favor of _DEFAULT_SOURCE.
_DEFAULT_SOURCE is included with _GNU_SOURCE, as well as _XOPEN_SOURCE >= 500,
so the obsolete and unnecessary definitions are removed.

For more details, see man 7 feature_test_macros for glibc >= 2.20.

Signed-off-by: Jan Ťulák <jtulak@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>