Add `long long` as an alias for `long`

parse.c

@@ -271,6 +271,8 @@ static Type *declspec(Token **rest, Token *tok) {
       break;
     case LONG:
     case LONG + INT:
+    case LONG + LONG:
+    case LONG + LONG + INT:
       ty = ty_long;
       break;
     default:

test/decl.c

@@ -8,6 +8,8 @@ int main() {
   ASSERT(8, ({ long int x; sizeof(x); }));
   ASSERT(8, ({ int long x; sizeof(x); }));
 
+  ASSERT(8, ({ long long x; sizeof(x); }));
+
   printf("OK\n");
   return 0;
 }