curl_easy_setopt.3: add CURLOPT_SSL_ENABLE_ALPN/NPN

(This option was known as CURLOPT_SSLKEYPASSWD up to 7.16.4 and

CURLOPT_SSLCERTPASSWD up to 7.9.2)

.IP CURLOPT_SSL_ENABLE_ALPN

Pass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. By

default, libcurl assumes a value of 1. This option enables/disables ALPN in

the SSL handshake (if the SSL backend libcurl is built to use supports it),

which can be used to negotiate http2.

(Added in 7.36.0)

.IP CURLOPT_SSL_ENABLE_NPN

Pass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. By

default, libcurl assumes a value of 1. This option enables/disables NPN in the

SSL handshake (if the SSL backend libcurl is built to use supports it), which

can be used to negotiate http2.

(Added in 7.36.0)

.IP CURLOPT_SSLENGINE

Pass a pointer to a zero terminated string as parameter. It will be used as

the identifier for the crypto engine you want to use for your private