When EWOULDBLOCK is not EAGAIN, treat it as equivalent to it

Acording to http://stackoverflow.com/questions/7003234/which-systems-define-eagain-and-ewouldblock-as-different-values
there are some older unixes that distinguish these error.s

event.c

@@ -2157,7 +2157,7 @@ evthread_notify_base_default(struct event_base *base)
 #else
 	r = write(base->th_notify_fd[1], buf, 1);
 #endif
-	return (r < 0 && errno != EAGAIN) ? -1 : 0;
+	return (r < 0 && ! EVUTIL_ERR_IS_EAGAIN(errno)) ? -1 : 0;
 }
 
 #ifdef EVENT__HAVE_EVENTFD

util-internal.h

@@ -79,15 +79,23 @@ extern "C" {
 
 #ifndef _WIN32
 
+#if EAGAIN == EWOULDBLOCK
+#define EVUTIL_ERR_IS_EAGAIN(e) \
+	((e) == EAGAIN)
+#else
+#define EVUTIL_ERR_IS_EAGAIN(e) \
+	((e) == EAGAIN || (e) == EWOULDBLOCK)
+#endif
+
 /* True iff e is an error that means a read/write operation can be retried. */
 #define EVUTIL_ERR_RW_RETRIABLE(e)				\
-	((e) == EINTR || (e) == EAGAIN)
+	((e) == EINTR || EVUTIL_ERR_IS_EAGAIN(e))
 /* True iff e is an error that means an connect can be retried. */
 #define EVUTIL_ERR_CONNECT_RETRIABLE(e)			\
 	((e) == EINTR || (e) == EINPROGRESS)
 /* True iff e is an error that means a accept can be retried. */
 #define EVUTIL_ERR_ACCEPT_RETRIABLE(e)			\
-	((e) == EINTR || (e) == EAGAIN || (e) == ECONNABORTED)
+	((e) == EINTR || EVUTIL_ERR_IS_EAGAIN(e) || (e) == ECONNABORTED)
 
 /* True iff e is an error that means the connection was refused */
 #define EVUTIL_ERR_CONNECT_REFUSED(e)					\