su_port.c etc: refactored su_port implementation.
Basic su_port.c implementation using pthreads and poll() is now divided into three modules: su_base_port.c contains base implementation with su_base_*() functions, su_pthread_port.c contains pthread-specific implementation and su_poll_port() contains poll()/epoll()-specific parts. The decomposed su_port allows implementations on different platforms and usages to share code as far as possible. This patch also introduces configure option --disable-poll-port which should be used on systems with emulated poll, like older *BSD derivatives such as OS X. Note however that su_select_poll.c is not completed yet. darcs-hash:20070126155634-65a35-09612536f51f7cd14c33ba42278bc9ed2cee4144.gz