va: Allow clean build on OpenBSD 6.6

[iarebatman]

These allow a clean, functional build on OpenBSD 6.6.
OpenBSD doesn't provide the same mechanism to get the
current thread id. Move existing TID references into
a new function get_pid_t and implement specifics there.

[dvrogozh]

Was that previously done by some custom patch during BSD packaging? If yes, can you, please, provide a link to the packaging scripts?

[iarebatman]

Was that previously done by some custom patch during BSD packaging? If yes, can you, please, provide a link to the packaging scripts?

It is not currently in the OpenBSD ports system. I'm currently putting a new port together and this
is my own patch.

[dvrogozh]

@iarebatman : thank you for clarification. I believe that while libva is not in OpenBSD, it presents in FreeBSD and they are dealing with basically the same issue. Here is their patch: https://svnweb.freebsd.org/ports/head/multimedia/libva/files/patch-va_va__trace.c?view=markup. Moreover, looking into it they are doing pretty the same as you do in this PR and it seems they thought about OpenBSD support:
https://svnweb.freebsd.org/ports/head/multimedia/libva/files/patch-va_va__trace.c?view=markup#l36. Can you, please, evaluate whether this change will work for you?

Anyhow, I believe we need to take FreeBSD effort into account and simplify everyone's live providing support for variety of operating systems. As of now FreeBSD patch seems to be more generic. I suggest to put it under review here. Would you mind to create corresponding PR or update this one?

[iarebatman]

@iarebatman : thank you for clarification. I believe that while libva is not in OpenBSD, it presents in FreeBSD and they are dealing with basically the same issue. Here is their patch: https://svnweb.freebsd.org/ports/head/multimedia/libva/files/patch-va_va__trace.c?view=markup. Moreover, looking into it they are doing pretty the same as you do in this PR and it seems they thought about OpenBSD support:
https://svnweb.freebsd.org/ports/head/multimedia/libva/files/patch-va_va__trace.c?view=markup#l36. Can you, please, evaluate whether this change will work for you?

Anyhow, I believe we need to take FreeBSD effort into account and simplify everyone's live providing support for variety of operating systems. As of now FreeBSD patch seems to be more generic. I suggest to put it under review here. Would you mind to create corresponding PR or update this one?

It does look like their patches would work. I will close this PR and create a new one.