try harder to get useconds_t from unistd.h

diff --git a/include/smpi/smpi.h b/include/smpi/smpi.h
index 490a9e7..a1ba3a0 100644 (file)
--- a/include/smpi/smpi.h
+++ b/include/smpi/smpi.h
@@ -6,7 +6,9 @@
 #ifndef SMPI_H
 #define SMPI_H
 
+#define __USE_XOPEN /* pick useconds_t in unistd.h */
 #include <unistd.h>
+
 #include <sys/time.h>
 #if _POSIX_TIMERS
 #include <time.h>