mod_reqtimeout: factorize structs and code.

With a bit of macro magic, this is to avoid more code duplication when adding
new stages (next commit will add TLS/handshake timeouts handling in addition to
existing header and body ones).

No functional change here.


mod_reqtimeout: Allow to configure (TLS-)handshake timeouts.

The timeouts apply between the process_connection and pre_read_request hooks.
They are disabled by default for compatibily reasons.


mod_reqtimeout: follow up to r1853906: adjust hooks priorities comments.


mod_reqtimeout: follow up to r1853901: fix macro args.


mod_reqtimeout: follow up to r1853901: init stage name outside INIT_STAGE().

It helps both code readability where stages are initilized and potential
logging in the input filter (even if the stage is disabled).


mod_http2: fix for latest mod_reqtimeout change re handshake timeouts

Submitted by: ylavic, icing
Reviewed by: ylavic, icing, jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1855409 13f79535-47bb-0310-9956-ffa450edef68