MFC r253513, r253542:

r253513:
 Create memstick images with the '.img' filename extension.

r253542:
 For consistency with previous releases, name the cdrom install
 cd 'disc1.iso'.

Approved by:	kib (mentor)
Approved by:	re (marius)
MFC r253541:
  Remove weirdly-named autofoo file.  This is not needed for the (FreeBSD)
  build, and freebsd-update chokes on it.

Approved by:	re (delphij)