From the commit message:

This earlier commit [1] from 2013 recognised the new names for programs
in dosfstools >= 3.0.18, specifically mkfs.fat and fsck.fat.  Now that
the oldest supported distributions use dosfstools >= 3.0.18 it is no
longer necessary to support using the old names of mkdosfs and dosfsck,
so remove that code.

    Oldest supported   Dosfstools
    distributions      Version

    Debian 8           3.0.27
    RHEL / CentOS 7    3.0.20
    SLES 12            3.0.26
    Ubuntu 14.04 LTS   3.0.26

[1] 1ae03dee953f512c0c664369db2d5e5db80b4058
    Recognise new dosfstools program names (#704629)

Plus a couple of small tidyup patches to ext2.cc.