Simple memory card reader program.

Controls :

Up       : Go up one file, the top file is the one found with firstfile().

Down     : Go down one file.

Left     : Select memory card slot 1.

Right    : Select memory card slot 2.

Circle   : Open current file for hex/ascii dump.

Triangle : Go up one 256 bytes block towards start of file.

Cross    : Go down one 256 bytes block towards end of file.

Square   : Display current file DIRENTRY.

Select   : Exit.

 The program starts with slot 2 selected, assuming a Yaroze configuration
with the access card in slot 1.

 It does not yet support >8k files, this because I defined BUFSIZE to be
8k and haven't bothered adding the read necessary when dealing with a
bigger file. It will be easily added or BUFSIZE changed !