improve trinary operator semantics

[cparser] / parsetest / cp_error018.c

int puts(const char *msg);

int main(int argc, char **argv)
{
        void *nu = 0;
        char *arg1 = argc > 1 ? argv[1] : 0;
        char *arg2 = argc <= 1 ? 0 : argv[1];
        char *arg3 = argc > 1 ? argv[1] : nu;
        char *arg4 = argc <= 1 ? nu : argv[1];

        if(arg1 != 0) {
                puts(arg1);
                puts(arg2);
                puts(arg3);
                puts(arg4);
        }

        return 0;
}