Added missing casts from lua_Unsigned to size_t

size_t can be smaller than lua_Usigned.

lstrlib.c

@@ -1811,8 +1811,8 @@ static int str_unpack (lua_State *L) {
         lua_Unsigned len = (lua_Unsigned)unpackint(L, data + pos,
                                           h.islittle, cast_int(size), 0);
         luaL_argcheck(L, len <= ld - pos - size, 2, "data string too short");
-        lua_pushlstring(L, data + pos + size, len);
-        pos += len;  /* skip string */
+        lua_pushlstring(L, data + pos + size, cast_sizet(len));
+        pos += cast_sizet(len);  /* skip string */
         break;
       }
       case Kzstr: {

lundump.c

@@ -109,7 +109,7 @@ static lua_Unsigned loadVarint (LoadState *S, lua_Unsigned limit) {
 
 
 static size_t loadSize (LoadState *S) {
-  return loadVarint(S, MAX_SIZE);
+  return cast_sizet(loadVarint(S, MAX_SIZE));
 }