Simpler implementation for tail calls

Tail calls handled by 'luaD_precall', like regular calls, to avoid
code duplication.

ldo.h

@@ -58,8 +58,8 @@ LUAI_FUNC int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 LUAI_FUNC void luaD_hook (lua_State *L, int event, int line,
                                         int fTransfer, int nTransfer);
 LUAI_FUNC void luaD_hookcall (lua_State *L, CallInfo *ci);
-LUAI_FUNC void luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func, int n);
-LUAI_FUNC CallInfo *luaD_precall (lua_State *L, StkId func, int nResults);
+LUAI_FUNC CallInfo *luaD_precall (lua_State *L, StkId func, int nresults,
+                                                            int delta1);
 LUAI_FUNC void luaD_call (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_callnoyield (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_tryfuncTM (lua_State *L, StkId func);