It isn't added as a separate protocol as HTTP2 will be done over HTTP://
URLs that can be upgraded to HTTP2 if the server supports it as well.
#define CURL_VERSION_CURLDEBUG (1<<13) /* debug memory tracking supported */
#define CURL_VERSION_TLSAUTH_SRP (1<<14) /* TLS-SRP auth is supported */
#define CURL_VERSION_NTLM_WB (1<<15) /* NTLM delegating to winbind helper */
+#define CURL_VERSION_HTTP2 (1<<16) /* HTTP2 support built-in */
/*
* NAME curl_version_info()