commit 8dd318ce162976c686bc9daa31ce191d59cb757c
Author: Ingo Korb <ingo@akana.de>
Date:   Sun Jan 24 20:21:49 2016 +0100

    doscmd: Check if partition is valid in U1/U2/B-R/B-W
    
    Reject accesses to invalid partition numbers in the block read/write
    commands. Resolves a crash of sd2iec when booting Necromancer.