Add tne necessary Makefiles and header files to facilitate building
MIT KRB5 as part of buildworld. Nothing will build until the
WITH_MITKRB5/MK_MITKRB5 option has been plumbed in Makefile.inc1.
Before any changes to Makefile.inc1 are made to enable MIT KRB5,
additional commits to other affected software will need to be committed.
Sponsored by: The FreeBSD Foundation
This group of patches is not enough to build MIT KRB5 within buildworld. Additional patches to openssh, pam_krb5, and other components are also needed. These will be submitted through other reviews.