- Move the nfds argument restriction to the nsysnet side.
- Allow user-defined FD_SETSIZE, since newlib's fd_set allow custom sizes.
- Define __socklen_t_defined when socklen_t is typedefed.
- __init/fini_wut_socket have been simplified and are now weak,
this is intended to allow users to customize their behaviour
- socket_lib_init/exit have been restored as regular imports and are
no longer using RPLWRAP
- __wut_socket_init/fini_devoptab are now exposed as global symbols,
intended to be used in custom socket init/deinit logic
