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.
