v1.3.1

OpenSSL v1.3.1

Merged pull requests:

• Few minor cleanups to eof/iswritable logic (#1) (@quinnj)
• Further cleanup on error handling and closing (#2) (@quinnj)
• Try to make closing SSLStream more race-stable (#3) (@quinnj)
• Fix a few more data races and a nonblocking issue in eof (#4) (@quinnj)
• Fix client-side verification handling to respect require_ssl_verifica… (#5) (@quinnj)
• Make sure we clear bio flags on each bio_stream_read callback (#6) (@quinnj)