Add support for a variadic ioctl() function.  The ioctl() interface is a non-standard, Unix interface.  NuttX has always used the older, three-parameter version.  Most contemporary systems now, however, use a variadic form of the ioctl() function.  Added an option to insert a shim layer to adapt the three-parameter ioctl() to use the variadic interface form.  Internally, the ioctl handling is the same three-parameter logic.  The only real complexity to the shim is in how the system calls must be handled.