Fix for the show­stop­per bug in the linuxulator

I got time yes­ter­day to test acrore­ad with the patch from Intron/Kostik and … Yeah! I was not able to crash acrore­ad in the 2.6.16 emu­la­tion! Great! Request for wide­spread test­ing soon?!?

Now we just have to deter­mine if we have to care about the lock­ing (I don’t know if kib@ already asked jhb@ about it) and the race con­di­tion. In case the user­land exhibits very very bad pro­gram­ming and is using the FD before open() returns suc­cess­ful­ly, the pro­gram could read data. This can only hap­pen if the pro­gram has the right per­mis­sion to this data (the open is sup­posed to fail in this case not because of access restric­tions, but because of e.g., the wrong file type).