do not eliminate varargs from functions that do not use varargs

(confuses the debug lib and gains very little in performance)

ldo.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ldo.c,v 2.151 2015/12/16 16:40:07 roberto Exp roberto $
+** $Id: ldo.c,v 2.152 2016/07/29 17:12:44 roberto Exp roberto $
 ** Stack and Call structure of Lua
 ** See Copyright Notice in lua.h
 */
@@ -374,13 +374,13 @@ int luaD_precall (lua_State *L, StkId func, int nresults) {
       int n = cast_int(L->top - func) - 1;  /* number of real arguments */
       int fsize = p->maxstacksize;  /* frame size */
       checkstackp(L, fsize, func);
-      if (p->is_vararg != 1) {  /* do not use vararg? */
+      if (p->is_vararg)
+        base = adjust_varargs(L, p, n);
+      else {  /* non vararg function */
         for (; n < p->numparams; n++)
           setnilvalue(L->top++);  /* complete missing arguments */
         base = func + 1;
       }
-      else
-        base = adjust_varargs(L, p, n);
       ci = next_ci(L);  /* now 'enter' new function */
       ci->nresults = nresults;
       ci->func = func;

lobject.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.h,v 2.115 2015/10/28 17:28:40 roberto Exp roberto $
+** $Id: lobject.h,v 2.116 2015/11/03 18:33:10 roberto Exp roberto $
 ** Type definitions for Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -407,7 +407,7 @@ typedef struct LocVar {
 typedef struct Proto {
   CommonHeader;
   lu_byte numparams;  /* number of fixed parameters */
-  lu_byte is_vararg;  /* 2: declared vararg; 1: uses vararg */
+  lu_byte is_vararg;
   lu_byte maxstacksize;  /* number of registers needed by this function */
   int sizeupvalues;  /* size of 'upvalues' */
   int sizek;  /* size of 'k' */

lparser.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lparser.c,v 2.153 2016/05/13 19:10:16 roberto Exp roberto $
+** $Id: lparser.c,v 2.154 2016/06/22 15:48:25 roberto Exp roberto $
 ** Lua Parser
 ** See Copyright Notice in lua.h
 */
@@ -766,7 +766,7 @@ static void parlist (LexState *ls) {
         }
         case TK_DOTS: {  /* param -> '...' */
           luaX_next(ls);
-          f->is_vararg = 2;  /* declared vararg */
+          f->is_vararg = 1;  /* declared vararg */
           break;
         }
         default: luaX_syntaxerror(ls, "<name> or '...' expected");
@@ -962,7 +962,6 @@ static void simpleexp (LexState *ls, expdesc *v) {
       FuncState *fs = ls->fs;
       check_condition(ls, fs->f->is_vararg,
                       "cannot use '...' outside a vararg function");
-      fs->f->is_vararg = 1;  /* function actually uses vararg */
       init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 1, 0));
       break;
     }
@@ -1614,7 +1613,7 @@ static void mainfunc (LexState *ls, FuncState *fs) {
   BlockCnt bl;
   expdesc v;
   open_func(ls, fs, &bl);
-  fs->f->is_vararg = 2;  /* main function is always declared vararg */
+  fs->f->is_vararg = 1;  /* main function is always declared vararg */
   init_exp(&v, VLOCAL, 0);  /* create and... */
   newupvalue(fs, ls->envn, &v);  /* ...set environment upvalue */
   luaX_next(ls);  /* read first token */