http: add --http2 to force HTTP/2
http: add --http2 to force HTTP/2

This is currently and transitionally used to test HTTP/2 over TLS.
Eventually, this should be done automatically.

Going forward, this will either be removed or used without TLS.

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc