net/freerdp1: Fix build with OpenSSL 1.1
Patch taken partially from upstream with some minor refactoring because
the patch from upstream was fairly far off from where this version of
FreeRDP is at.
Built with: Poudriere (11.2 and 13.0-CURRENT)
Tested with: OpenSSL 1.0.2 (11.2, base)
Tested with: OpenSSL 1.1.1 (11.2, security/openssl111)
PR: 233014
Approved by: ultima (ports), myself (maintainer)
MFH: 2018Q4 (OpenSSL build fix)