pkg/51486: pkgsrc on OpenBSD should prefer pkgsrc openssl

[Jonathan%NetBSD.org@localhost,Schleifer%NetBSD.org@localhost]

>Number:         51486
>Category:       pkg
>Synopsis:       pkgsrc on OpenBSD should prefer pkgsrc openssl
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Sun Sep 18 13:10:00 +0000 2016
>Originator:     js-pkgsrc%heap.zone@localhost
>Release:        HEAD
>Organization:
>Environment:
OpenBSD obsdvm.localdomain 6.0 GENERIC.MP#2319 amd64
>Description:
OpenBSD is not shipping with OpenSSL anymore, but with LibreSSL. Over the time, slight API differences have developed. As OpenBSD used to ship with OpenSSL, pkgsrc prefers native OpenSSL over pkgsrc OpenSSL. As that native OpenSSL is LibreSSL in fact, things break.
>How-To-Repeat:

>Fix:
Add _OPSYS_PREFER.openssl ?= pkgsrc to mk/platform/OpenBSD.mk