mke2fs: recognize mke4fs program name

mke2fs: recognize mke4fs program name

We shipped "mke4fs" alongside mke2fs in RHEL5, so that ext4-capable
utilities could be installed without disturbing the venerable e2fsprogs-1.39
shipped in RHEL5 from the beginning.  But it surprised some users that
"mke4fs" created ext2 filesystems by default rather than ext4.
While it was my intent to have the renamed binaries behave exactly
like the stock ones, it seems that there is some precedence for
handling "mkeNfs" in the code, so seems reasonable to add
mke4fs -> ext4 as well.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>