Merge r1697855, r1697339, r1696428, r1696266, r1696264, r1695874, r1695727,...

Merge r1697855, r1697339, r1696428, r1696266, r1696264, r1695874, r1695727, r1692516, r1692486, r1610674, r1685069, r1693918, r1698116, r1698133, r1694950, r1700968, r1701005, r1701145, r1701178 from trunk:

adding ap_get_protocol(c) which safeguards against NULL returns, for use instead of direct calling ap_run_protocol_get

changed Protocols to let vhosts override servers, removed old H2Engine example from readme

creating ap_array_index in util, forwarding scheme into request processing, enabling SSL vars only when scheme is not http:, delayed connection creation until task worker assignment

removed unnecessary lingering_close and sbh update on end of protocol upgrade handling

introducing ap_array_index in util, used in protocol and mod_h2

fixes existing protocol missing in selection if not explicitly proposed

new directive ProtocolsHonorOrder, added documentation for Protocols feature, changed preference selection and config merging

removed accidental code

new Protocols directive and core API cha...