fix

fixes error

include/socket.c: In function ‘set_socket_nonblocking’:
include/socket.c:202:25: error: ‘F_SETFL’ undeclared (first use in this function)
     if(fcntl(socket_fd, F_SETFL, O_NONBLOCK) == -1)
                         ^
include/socket.c:202:25: note: each undeclared identifier is reported only once for each function it appears in
include/socket.c:202:34: error: ‘O_NONBLOCK’ undeclared (first use in this function)
     if(fcntl(socket_fd, F_SETFL, O_NONBLOCK) == -1)