External strings

Strings can use external buffers to store their contents.

lua.h

@@ -244,6 +244,8 @@ LUA_API void        (lua_pushnil) (lua_State *L);
 LUA_API void        (lua_pushnumber) (lua_State *L, lua_Number n);
 LUA_API void        (lua_pushinteger) (lua_State *L, lua_Integer n);
 LUA_API const char *(lua_pushlstring) (lua_State *L, const char *s, size_t len);
+LUA_API const char *(lua_pushextlstring) (lua_State *L,
+		const char *s, size_t len, lua_Alloc falloc, void *ud);
 LUA_API const char *(lua_pushstring) (lua_State *L, const char *s);
 LUA_API const char *(lua_pushvfstring) (lua_State *L, const char *fmt,
                                                       va_list argp);