[Fractdev] Building xfractint fails with -fno-common or gcc 10

Dear xfractint developers, I'm a gentoo linux user and it has been noticed that xfractint does not compile with -fno-common or gcc-10 (https://bugs.gentoo.org/706522). I'm not a C programmer, but I've managed to get the software to compile by applying the three attached patches. Please let me know if you intend to modify your source code so that I know what to do with the corresponding gentoo package. Best regards, David Denoncin.