lua: Optional commas.

From: http://lua-users.org/lists/lua-l/2012-03/msg00175.html
Allows optional commas for consecutive "key" = value fields. This is common in Configi promise bodies.
file.touch {
  path = "/tmp/test"
  comment = "touching file"
}

vendor/lua/lparser.c

@@ -637,18 +637,30 @@ struct ConsControl {
 };
 
 
-static void recfield (LexState *ls, struct ConsControl *cc) {
-  /* recfield -> (NAME | '['exp1']') = exp1 */
+static void namedfield (LexState *ls, struct ConsControl *cc) {
+  /* namedfield -> (NAME '=' exp) */
   FuncState *fs = ls->fs;
   int reg = ls->fs->freereg;
   expdesc key, val;
   int rkkey;
-  if (ls->t.token == TK_NAME) {
-    checklimit(fs, cc->nh, MAX_INT, "items in a constructor");
-    checkname(ls, &key);
-  }
-  else  /* ls->t.token == '[' */
-    yindex(ls, &key);
+  checklimit(fs, cc->nh, MAX_INT, "items in a constructor");
+  checkname(ls, &key);
+  cc->nh++;
+  checknext(ls, '=');
+  rkkey = luaK_exp2RK(fs, &key);
+  expr(ls, &val);
+  luaK_codeABC(fs, OP_SETTABLE, cc->t->u.info, rkkey, luaK_exp2RK(fs, &val));
+  fs->freereg = reg;  /* free registers */
+}
+
+
+static void kfield (LexState *ls, struct ConsControl *cc) {
+  /* kfield -> ('[' exp ']' '=' exp) */
+  FuncState *fs = ls->fs;
+  int reg = ls->fs->freereg;
+  expdesc key, val;
+  int rkkey;
+  yindex(ls, &key);
   cc->nh++;
   checknext(ls, '=');
   rkkey = luaK_exp2RK(fs, &key);
@@ -658,6 +670,23 @@ static void recfield (LexState *ls, struct ConsControl *cc) {
 }
 
 
+static void recfields (LexState *ls, struct ConsControl *cc) {
+  /* recfields -> (`['exp`] = exp' | NAME = exp {NAME = exp})*/
+  if(ls->t.token == '[')
+    kfield(ls, cc);
+  else if(ls->t.token == TK_NAME) {
+    do {
+      namedfield(ls, cc);
+    } while(ls->t.token == TK_NAME);
+  } else {
+    lua_assert(0); /* not entirely sure this can be reached */
+  }
+  check_condition(ls,
+      ls->t.token == '}' | ls->t.token == ',' | ls->t.token == ';',
+      "expected separator (',' | ';') or '}'");
+}
+
+
 static void closelistfield (FuncState *fs, struct ConsControl *cc) {
   if (cc->v.k == VVOID) return;  /* there is no list item */
   luaK_exp2nextreg(fs, &cc->v);
@@ -700,11 +729,11 @@ static void field (LexState *ls, struct ConsControl *cc) {
       if (luaX_lookahead(ls) != '=')  /* expression? */
         listfield(ls, cc);
       else
-        recfield(ls, cc);
+        recfields(ls, cc);
       break;
     }
     case '[': {
-      recfield(ls, cc);
+      kfield(ls, cc);
       break;
     }
     default: {