thread entrypoints:
(lwpSelect, shutdown_sequence): Parameters didn't match thread entry
point prototype.
(lwpEntryPoint): Arguments didn't match thread entry point prototype.
Change linkage of functions without prototype declaration to static
where possible.
Remove some superflous declarations, replace others by suitable
includes.
(io_select, io_flush, io_iopfromfd): Unused, remove.
(io_open): Allow more than one open for the same file descriptor.
The check is the last remaining use of io_list[], and it's
unimportant.
(io_list, niop, io_init): io_list[] no longer serves any purpose,
remove. Sparse allocation of file descriptors (deplorable misfeature
of Winsock, at least some versions) is no longer a problem.
(getfdtablesize): Unused, remove. Was broken for Windows anyway.
io_list[] indexing.
(niop, io_init): Store length of io_list[] in new niop.
(player_accept): Checking the socket file descriptor here is now
redundant. Remove.
io_puts, iom_create, iom_getmask, iom_set, iom_clear, iom_zero):
Portability bug: io_select() passed bit_fdmask to select(). This
breaks the fd_set abstraction, and works only with the traditional
Unix implementation of fd_set. Use fd_set and its operations instead.
Remove unused source files. Note: the offending code is currently
unsued. But it's a time bomb, and fixing it also replaces a bunch of
code by standard library services.
