ports/pkg incompatibility, os/libc api changes

[Norbert Koch]

Hello.

I am observing this on a system running FreeBSD 9.1:

If I build fontconfig from ports all is ok.

If I do pkg install fontconfig it does not work.

The reason is that fontconfig calls fcntl()
with the parameter F_DUPFD_CLOEXEC. This has
been introduced afaics since FreeBSD 9.2.

So, I obviously should update to 9.3 and all would be ok,
but, due to different reasons, this is not a solution for me.

My question is:

Is it, according to FreeBSD policies,
acceptable to change the os (or libc) api without
changing FreeBSD's major version number?

If yes, is there some documentation about potential
problems like the one I found?
Shouldn't pkg reject to install an incompatible package?

Best regards,
Norbert Koch