Merge r1697855, r1697339, r1696428, r1696266, r1696264, r1695874, r1695727, r1692516...

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 changes to enable protocol switching on HTTP Upgrade or ALPN, implemented in mod_ssl and mod_h2

SECURITY (CVE-2014-0117): Fix a crash in mod_proxy.  In a reverse
proxy configuration, a remote attacker could send a carefully crafted
request which could crash a server process, resulting in denial of
service.

Thanks to Marek Kroemeke working with HP's Zero Day Initiative for
reporting this issue.

* server/util.c (ap_parse_token_list_strict): New function.

* modules/proxy/proxy_util.c (find_conn_headers): Use it here.

* modules/proxy/mod_proxy_http.c (ap_proxy_http_process_response):
  Send a 400 for a malformed Connection header.

Submitted by: Edward Lu, breser, covener

http, mod_ssl: Introduce and return the 421 (Misdirected Request) status code
for clients requesting a hostname on a reused connection whose SNI (from the
TLS handshake) does not match.
PR 5802.

This allows HTTP/2 clients to fall back to a new connection as per:
https://tools.ietf.org/html/rfc7540#section-9.1.2

Proposed by: Stefan Eissing <stefan eissing.org>
Reviewed by: ylavic

c89

Allowing protocol_propose hooks to be called with offers=NULL, clarifying semantics as proposed by chaosed0@gmail.com

giving ap_array_index a start parameter, adding ap_array_contains

ap_process_request needs exportation for use in mod_h2 on Windows

final final change to the new ap_array_str_* functions after review

changed Protocols default to http/1.1 only, updated documentation, changed ap_select_protocol() to return NULL when no protocol could be agreed upon

mod_ssl: fix compiler warning (bad cast).

improvements in ap_select_protocol(), supplied by yann ylavic
Submitted by: icing, jorton, ylavic, covener, icing, icing, gsmith, icing, icing, ylavic, icing
Reviewed/backported by: jim

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1705672 13f79535-47bb-0310-9956-ffa450edef68