NAME
       AllocXtra -- allocate and initialise a valid BlitzXtra structure.

   SYNOPSIS
       xtraFile = AllocXtra();
       D0

       struct BlitzXtra * AllocXtra(VOID);

   FUNCTION
       This command allocates a new BlitzXtra structure, filling fields
       with default values.

   INPUTS
       NONE

   RESULT
       xtraFile - an initialized BlitzXtra structure, or NULL on failure.

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