Use constructor attribute on non-Solaris platforms.

Index: zfs+chaos4/lib/libuutil/uu_misc.c
===================================================================
--- zfs+chaos4.orig/lib/libuutil/uu_misc.c
+++ zfs+chaos4/lib/libuutil/uu_misc.c
@@ -251,7 +251,13 @@ uu_release_child(void)
 	uu_release();
 }
 
+#ifdef __GNUC__
+static void
+uu_init(void) __attribute__((constructor));
+#else
 #pragma init(uu_init)
+#endif
+
 static void
 uu_init(void)
 {
Index: zfs+chaos4/lib/libzfs/libzfs_mount.c
===================================================================
--- zfs+chaos4.orig/lib/libzfs/libzfs_mount.c
+++ zfs+chaos4/lib/libzfs/libzfs_mount.c
@@ -128,7 +128,13 @@ zfs_share_proto_t share_all_proto[] = {
 	PROTO_END
 };
 
+#ifdef __GNUC__
+static void
+zfs_iscsi_init(void) __attribute__((constructor));
+#else
 #pragma init(zfs_iscsi_init)
+#endif
+
 static void
 zfs_iscsi_init(void)
 {
@@ -548,8 +554,12 @@ static void (*_sa_update_sharetab_ts)(sa
  * values to be used later. This is triggered by the runtime loader.
  * Make sure the correct ISA version is loaded.
  */
-
+#ifdef __GNUC__
+static void
+_zfs_init_libshare(void) __attribute__((constructor));
+#else
 #pragma init(_zfs_init_libshare)
+#endif
 static void
 _zfs_init_libshare(void)
 {