Kris Katterjohn authored Dec 23, 2018 and Nick Mathewson committed Jan 09, 2019

Prior to this commit, the testsuite was failing on OpenBSD.  After
this commit the testsuite runs fine on OpenBSD.

It was previously decided to test for the OpenBSD macro (rather than
__OpenBSD__, etc.) because OpenBSD forks seem to have the former
macro defined.  sys/param.h must be included for the OpenBSD macro
definition; however, many files tested for the OpenBSD macro without
having this header included.

This commit includes sys/param.h in the files where the OpenBSD macro
is used (and sys/param.h is not already included), and it also
changes some instances of the __OpenBSD__ macro to OpenBSD.

See commit 27df23ab which changed
everything to use OpenBSD instead of __OpenBSD__ or OPENBSD.  See
also tickets #6982 and #20980

 (the latter ticket is where it was
decided to use the OpenBSD macro).

Signed-off-by: Kris Katterjohn <katterjohn@gmail.com>