Update to 5.50

Changelog:
Version 5.50, 2018.12.02, urgency: MEDIUM
* New features
  - 32-bit Windows builds replaced with 64-bit builds.
  - OpenSSL DLLs updated to version 1.1.1.
  - Check whether "output" is not a relative file name.
  - Major code cleanup in the configuration file parser.
  - Added sslVersion, sslVersionMin and sslVersionMax
    for OpenSSL 1.1.0 and later.
* Bugfixes
  - Fixed PSK session resumption with TLS 1.3.
  - Fixed a memory leak in WIN32 logging subsystem.
  - Allow for zero value (ignored) TLS options.
  - Partially refactored configuration file parsing
    and logging subsystems for clearer code and minor
        bugfixes.
* Caveats
  - We removed FIPS support from our standard builds.
    FIPS will still be available with bespoke builds.

(ryoon)