Various build fixes for OpenBSD

Submitted by Jasper Lievisse Adriaanse

Assigned to Simon McVittie

Link to original bug (#30347)

Description

Created attachment 38903 Various build fixes

• Include the right headers needed, at the right location (system headers before uerland headers)
• Locally define SCM_CREDENTIALS and SO_PASSCRED. This is rather ugly, and I'm not even sure this actually works. Any idea?
• OpenBSD's ucred structure doesn't have a pid member.

Diff attached fixes the build.

Attachment 38903, "Various build fixes":
gibber_obsd.diff