Bug#508933: Patch for joystick support for gravitywars

[Steve Cotton]

It's not obvious how to calibrate the joystick and the defaults
work badly with my joypad (only recognises down and right by
default).

<stevecotton> ah, the -j command line option allows calibration
    of the joystick, and then it works
<stevecotton> ./GravityWars101.c:
    printf ("Can not load joystick configuration file. Using defaults.\n");
<stevecotton> It does print that when run without joystick
    settings, but a hint about how to set it (and a clue for
    people starting it from a WM menu) would be good.
<bdefreese> Hmm, where to put the -j option.  In the manpage?


The command-line parsing in GravityWars101.c would be cleaner if
the game always recognised the -j option; and then quit with an
error if it had been compiled without joystick support.

Steve