Fix Lua link order

Put -llua* in LIBS rather than LDFLAGS to get correct link order.
Without this the configure test for Lua fails when using GCC 4.6,
the default compiler on recent Linux distributions like Ubuntu
11.10.

auxdir/x_ac_lua.m4

@@ -22,9 +22,9 @@ AC_DEFUN([X_AC_LUA],
 
 	if test "x$x_ac_have_lua" = "xyes"; then
 	  saved_CFLAGS="$CFLAGS"
-	  saved_LDFLAGS="$LDFLAGS"
+	  saved_LIBS="$LIBS"
 	  CFLAGS="$CFLAGS $lua_CFLAGS"
-	  LDFLAGS="$LDFLAGS $lua_LIBS"
+	  LIBS="$LIBS $lua_LIBS"
 	  AC_MSG_CHECKING([for whether we can link to liblua])
 	  AC_TRY_LINK(
 		[#include <lua.h>
@@ -37,7 +37,7 @@ AC_DEFUN([X_AC_LUA],
 
 	  AC_MSG_RESULT([$x_ac_have_lua])
 	  CFLAGS="$saved_CFLAGS"
-	  LDFLAGS="$saved_LDFLAGS"
+	  LIBS="$saved_LIBS"
 	fi
 
 	AM_CONDITIONAL(HAVE_LUA, test "x$x_ac_have_lua" = "xyes")