Fix CVE-2014-5461 for Lua 5.1 (#6)

This fixes stack overflow in vararg functions

Author: khvzak

lua-5.1.5/ldo.c

@@ -274,7 +274,7 @@ int luaD_precall (lua_State *L, StkId func, int nresults) {
     CallInfo *ci;
     StkId st, base;
     Proto *p = cl->p;
-    luaD_checkstack(L, p->maxstacksize);
+    luaD_checkstack(L, p->maxstacksize + p->numparams);
     func = restorestack(L, funcr);
     if (!p->is_vararg) {  /* no varargs? */
       base = func + 1;
@@ -366,7 +366,7 @@ int luaD_poscall (lua_State *L, StkId firstResult) {
 ** The arguments are on the stack, right after the function.
 ** When returns, all the results are on the stack, starting at the original
 ** function position.
-*/ 
+*/
 void luaD_call (lua_State *L, StkId func, int nResults) {
   if (++L->nCcalls >= LUAI_MAXCCALLS) {
     if (L->nCcalls == LUAI_MAXCCALLS)