ustream-io-cyassl.c: fix client-mode connections

ustream-io-cyassl.c: fix client-mode connections

Starting in v3.13.2, wolfSSL stores the BIO send and recv callbacks
in the SSL struct.  When the SSL session is created, it inherits the
calls from the SSL_CTX, but they do not get updated when the SSL_CTX
callbacks are changed.

Currently, ustream-ssl sets the callbacks after the SSL session is
created, causing failures.  Client apps, such as uclient-fetch fail
immediately to connect to https URLs with a 'Connection failed' error
message.  uhttpd seems unaffected.

New calls to set them directly to the SSL struct were added in 4.1.0, so
we can use them, with a check in CMakeLists.txt to detect their
presence.  Otherwise, another call to ustream_set_io is done before
creating the SSL session to properly set the callbacks.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>