_XOPEN_SOURCE not needed for usleep() in Solarish systems.

*** 12,22 ****
--- 12,24 ----
   * express or implied. See the License for the specific language governing
   * permissions and limitations under the License.
   */
  
  /* Use usleep */
+ #ifndef __sun
  #define _XOPEN_SOURCE 500
+ #endif /* __sun doesn't need XOPEN_SOURCE defined for usleep() in unistd.h. */
  #include <unistd.h>
  
  #include <errno.h>
  #include <s2n.h>