Previous minimum was: 1.2.4 (2002-02-28)
- assume `gssapi/gssapi.h` header for MIT Kerberos.
Drop logic detecting this header, and drop alternate logic including
a bare "gssapi.h". Bare `gssapi.h` is Heimdal-specific. MIT Kerberos
added support for it for Heimdal compatibility on 2006-11-09,
redirecting to `gssapi/gssapi.h`. MIT Kerberos supported the latter
header in the 1990s already.
Ref: 40e1a016f9 (2008-03-06)
Ref: d119352001 (2006-11-09)
- configure.ac: stop using `HAVE_GSSAPI_GSSAPI_H`.
Added in 2010 to support "ancient distros such as RHEL-3" where
`gssapi/gssapi_krb5.h` did not include `gssapi/gssapi.h`.
MIT Kerberos includes it since commit:
d9e959edfa (2003-03-06)
Released in 1.3 (2003-07-08).
Bump minimum required version to avoid this issue.
Reverts cca192e58f (2010-04-16)
Ref: https://web.mit.edu/kerberos/dist/historic.html
Ref: https://sources.debian.org/src/krb5/Closes#18992
0855f30709