lua_tag bug

["Paul Hankin" <phankin@...>]

lua_tag should return LUA_NOTAG (-2) when given a non-valid index, but
actually returns -1.

lapi.c: 134c134
<                                 luaT_effectivetag(L, o)), -1);
---
>                                 luaT_effectivetag(L, o)), LUA_NOTAG);

--
Paul Hankin