new API function 'lua_mainthread'

lapi.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lapi.c,v 2.76 2009/04/17 22:00:01 roberto Exp roberto $
+** $Id: lapi.c,v 2.78 2009/06/01 19:09:26 roberto Exp roberto $
 ** Lua API
 ** See Copyright Notice in lua.h
 */
@@ -99,6 +99,11 @@ LUA_API int lua_checkstack (lua_State *L, int size) {
 }
 
 
+LUA_API lua_State *lua_mainthread (lua_State *L) {
+  return G(L)->mainthread;
+}
+
+
 LUA_API void lua_xmove (lua_State *from, lua_State *to, int n) {
   int i;
   if (from == to) return;