blaze_util_posix.cc: declare use of dprintf
On some systems, the dprintf header is only part of <stdio.h> if
requested (to allow compatibility with applications before the
standardization of dprintf). As we use dprintf, request it
by defining _WITH_DPRINTF.
// See the License for the specific language governing permissions and
// limitations under the License.
+#define _WITH_DPRINTF
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
