mk_plugin_next: Add mk_body_redirect().

Set headers for 3** responses.
mk_plugin_next: Add mk_resolve_file().

Resolves file path, opens and stat file.
static: Use mk_resolve_file() and mk_body_redirect().
mk_plugin_next: Rename struct request_info -> struct mk_request_info.
mk_plugin_next: FIxup, add mk_event_socket() to header.
mk_plugin: Always call _mkp_event_close() and inc accepted connections.
mk_plugin: Fixup for connection hooks.

Ignore close if owned by event handlers.
Call mk_sched_remove_client() on plugin event fd.
mk_epoll: Use bit fields for events.

This converts MK_EPOLL_* values into bit fields.
mk_epoll: Store state in sched_connection.

Use bit fields to store the epoll in the sched_connection.
Add sched_connection argument to mk_epoll_add(), mk_epoll_del() and
mk_epoll_change_mode().
Remove mode argument from mk_epoll_add() and mk_epoll_change_mode().
Remove all mk_epoll_state, sleep/wakeup state is stored in
sched_connection.
mk_scheduler: Arguments of epoll functions changed.
mk_http: Arguments for epoll functions changed.
mk_socket: Arguments of epoll functions changed.
monkey: Don't initialize epoll state.
mk_plugin: Arguments of epoll functions changed.
Merge branch 'event_sleep' into plugin_next
mk_queue: Add mk_queue_move_all() and mk_queue_reset().
mk_filter: Add content filtering module.
mk_queue: Fix mk_queue_string().

Incorrectly discarded offset when part of entry consumed.
mk_request: Add filtering support members and states.

Three new states,

* MK_REQUEST_FILTER - Neither body nor header filter done.
* MK_REQUEST_FILTER_HEADER - Header filter not done.
* MK_REQUEST_FILTER_BODY - Body filter not done.
mk_filter: Fixup of filtering module.