NAME
       SaveXtra -- save a .xtra file to disk

   SYNOPSIS
       success = SaveXtra(fileName, xtraFile);
       D0                 A0        A1

       BOOL success = SaveXtra(char * fileName, struct BlitzXtra * xtraFile);

   FUNCTION
       This function will save a valid BlitzXtra structure to disk in the form
       of a standard Blitz .xtra file.

   INPUTS
       fileName - a null-terminated string containing the name of the .xtra file
                  to save

       xtraFile - a pointer to a valid BlitzXtra structure

   RESULT
       success - an indication of success or failure

   SEE ALSO
        AllocXtra(),  FreeXtra(),  LoadXtra(), <libraries/blitz.h>, <libraries/blitz.i>