https://www.openssl.org/docs/crypto/threads.html#DESCRIPTION
https://curl.haxx.se/libcurl/c/opensslthreadlock.html
+
+For OpenSSL versions starting with 1.1.0, no particular action is required.
.IP GnuTLS
http://gnutls.org/manual/html_node/Thread-safety.html
.IP NSS
The engine is used by libcurl in a way that is fully thread-safe.
.IP wolfSSL
The engine is used by libcurl in a way that is fully thread-safe.
+.IP BoringSSL
+The engine is used by libcurl in a way that is fully thread-safe.
.SH "Other areas of caution"
.IP Signals
Signals are used for timing out name resolves (during DNS lookup) - when built