Send len bytes from buf to dest_addr

Property definitions

socket $ NativeSocket :: sendto
	# Send `len` bytes from `buf` to `dest_addr`
	fun sendto(buf: CString, len: Int, flags: Int, dest_addr: NativeSocketAddrIn): Int `{
		return sendto(*self, buf, len, flags, (struct sockaddr*)dest_addr, sizeof(struct sockaddr_in));
	`}
lib/socket/socket_c.nit:246,2--249,3