Rocks'n'Diamonds

I would have put this in bugzilla, but I couldn't quite figure out how to get an account there, so I'll put it here instead.

Fedora 32 will use GCC 10, which sets -fno-common by default. This broke the rocks'n'diamonds compile, because the following variables are defined in multiple places:

struct SetupInfo setup;
int GfxFrame[MAX_LEV_FIELDX][MAX_LEV_FIELDY];

The attached patch comments them out of src/main.c and resolves the issue.

Fixed! (Not in the Git repo yet...)

Did you encounter any other bugs or warnings when using gcc10?

(I think I should set up a little VM with gcc10 and check for myself... )

P.S.: Regarding Bugzilla, I currently only set up accounts on demand, as I fear lots of spam if I open it up publicly for registration (because it does not offer any effective SPAM counter measures, unfortunately).