Define away spa_event_notify() in userspace - not necessary and breaks compilation in older Solaris builds.

Index: zfs+chaos4/lib/libzfscommon/include/sys/spa.h
===================================================================
--- zfs+chaos4.orig/lib/libzfscommon/include/sys/spa.h
+++ zfs+chaos4/lib/libzfscommon/include/sys/spa.h
@@ -516,7 +516,11 @@ extern int spa_prop_get(spa_t *spa, nvli
 extern void spa_prop_clear_bootfs(spa_t *spa, uint64_t obj, dmu_tx_t *tx);
 
 /* asynchronous event notification */
+#ifdef _KERNEL
 extern void spa_event_notify(spa_t *spa, vdev_t *vdev, const char *name);
+#else
+#define spa_event_notify(s,v,n) ((void) 0)
+#endif
 
 #ifdef ZFS_DEBUG
 #define	dprintf_bp(bp, fmt, ...) do {				\
Index: zfs+chaos4/lib/libzpool/spa.c
===================================================================
--- zfs+chaos4.orig/lib/libzpool/spa.c
+++ zfs+chaos4/lib/libzpool/spa.c
@@ -4449,10 +4449,10 @@ spa_has_spare(spa_t *spa, uint64_t guid)
  * in the userland libzpool, as we don't want consumers to misinterpret ztest
  * or zdb as real changes.
  */
+#ifdef _KERNEL
 void
 spa_event_notify(spa_t *spa, vdev_t *vd, const char *name)
 {
-#ifdef _KERNEL
 	sysevent_t		*ev;
 	sysevent_attr_list_t	*attr = NULL;
 	sysevent_value_t	value;
@@ -4497,8 +4497,8 @@ done:
 	if (attr)
 		sysevent_free_attr(attr);
 	sysevent_free(ev);
-#endif
 }
+#endif
 
 void
 spa_discard_io(spa_t *spa)