#most of fix from here http://postgis.refractions.net/pipermail/postgis-devel/2009-February/004879.html
--- pllua-0.3.1/plluaapi.c.orig	Thu Sep 17 15:34:07 2009
+++ pllua-0.3.1/plluaapi.c	Thu Sep 17 15:34:18 2009
@@ -7,6 +7,10 @@
 
 #include "pllua.h"
 #include "rowstamp.h"
+#include "utils/guc.h"
+extern Datum textout (PG_FUNCTION_ARGS);
+extern Datum bpcharout(PG_FUNCTION_ARGS);
+extern Datum varcharout(PG_FUNCTION_ARGS);
 
 /* extended function info */
 typedef struct luaP_Info {