GetCrc32 ( cFileName ) -> cHexCrc32

   This function will give you the CRC32-checksum of any file.
   Returns an 8-digit HexString to Clipper.
   CRC32 polynomial = edb88320h, these values are identical with
   the CRC32-checksums of PKzip and FileScan!
   If an errors occurs, maybe the file does not exist (?) or any
   read error, '00000000' is returned.

   PARAMETER:
   cFileName   the name of the file to build the checksum for.

   RETURN VALUES:
   8-digit HexString containing the CRC32-checksum

   EXAMPLE:

         GetCrc32 ("asmFont.016") -> "5D61B923"