[Midnightbsd-cvs] src: mkfs.c: Stop trying to zero UFS1 superblocks if we fall off the end

[laffer1 at midnightbsd.org]

Log Message:
-----------
Stop trying to zero UFS1 superblocks if we fall off the end of the disk or hit random partial data that looks like a superblock.

Obtained from: FreeBSD

Modified Files:
--------------
    src/sbin/newfs:
        mkfs.c (r1.5 -> r1.6)
        (http://cvsweb.midnightbsd.org/src/sbin/newfs/mkfs.c?r1=1.5&r2=1.6)