core13: An Arduino core for the Attiny13 *testers wanted*

Hi guys, I'm trying to use the ledControl library for the MAX7219 led driver but the sketch does not complile.
After a little search I've found that variables of this kind

B01111110

are not recognized.
No problems with ATtiny85/84/2313 core.
Do you know if it is easy to fix this?
If it may be usefull I am using IDE 0022 under kubuntu 11.04.
Thanks.