NAME
       GetLineHeaderSize -- get the size of the header prepended to Blitz source
                            code

   SYNOPSIS
       size = GetLineHeaderSize();
       D0

       UWORD size = GetLineHeaderSize(VOID);

   FUNCTION
       The standard Blitz line structure was fixed at 9 bytes. This consisted of
       the usual Previous and Next pointers, as well as a byte indicating how
       many characters are on the line. From v2.2 onwards, an extra control field
       was inserted to allow procedure folding. To improve backwards compatibility
       or programs it is necessary to know how large this header is. It can be
       assumed that the following fields remain static :

           NEXT           0
           PREVIOUS       4
           NUMCHARS       HEADERSIZE-1
           CHARS          HEADERSIZE

       This allows additional fields to be inserted without risking incompatibility
       with older software.

   INPUTS
       NONE

   RESULT
       size - the number of bytes which make up the line header