Initial work to determine the protocol of a socket, before it is accept()'ed.

If we can determine the protocol at startup when we allocate the socket, the correct Accept Filters can be applied. Currently we blindly apply the http accept filter.

* server/core.c: Add 'Protocol' to the core module config
* server/core.c: Add ap_{set,get}_server_protocol API.
* server/listen.c: Attempt to inherit protocols from Listener Records to Server configs.
                   I do not like the current code, but it works.
* server/listen.c: The 'Listen' directive can now optionally take a protocol arg
* include/{ap_listen.h,http_core.h}: Add Protocol to respective structures.
* include/ap_mmn.h: Minor MMN Bump for the new interfacces.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/listen-protocol@168459 13f79535-47bb-0310-9956-ffa450edef68