* made epoll() support a compile-time option : ENABLE_EPOLL
* provided a very little libc replacement for a possibly missing epoll()
implementation which can be enabled by -DUSE_MY_EPOLL
* implemented the poll() poller, which can be enabled with -DENABLE_POLL.
The equivalent runtime argument becomes '-P'. A few tests show that it
performs like select() with many fds, but slightly slower (certainly
because of the higher amount of memory involved).
* separated the 3 polling methods and the tasks scheduler into 4 distinct
functions which makes the code a lot more modular.
* moved some event tables to private static declarations inside the poller
functions.
* the poller functions can now initialize themselves, run, and cleanup.
* changed the runtime argument to enable epoll() to '-E'.
* removed buggy epoll_ctl() code in the client_retnclose() function. This
function was never meant to remove anything.
* fixed a typo which caused glibc to yell about a double free on exit.
* removed error checking after epoll_ctl(DEL) because we can never know if
the fd is still active or already closed.
* added a few entries in the makefile
willy tarreau