Revert "Drop support for Glib <2.32"

This reverts commit e9a0c53bdb.

pluma/pluma.c

@@ -560,6 +560,11 @@ main (int argc, char *argv[])
 	g_type_init ();
 #endif
 
+	/* Init glib threads asap */
+#if !GLIB_CHECK_VERSION (2, 32, 0)
+	g_thread_init (NULL);
+#endif
+
 	/* Setup debugging */
 	pluma_debug_init ();
 	pluma_debug_message (DEBUG_APP, "Startup");