Fix gcc init pragma warnings

Use constructor attribute on non-Solaris platforms.

The #pragma init/fini ->__attribute__((constructor/destructor))
conversions, these should go upstream.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

lib/libuutil/uu_misc.c

@@ -249,7 +249,13 @@ 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)
 {

lib/libzfs/libzfs_mount.c

@@ -518,8 +518,12 @@ static void (*_sa_update_sharetab_ts)(sa_handle_t);
  * 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)
 {