Keep polling for events until there isn't any

src/unix/unix.c

@@ -990,7 +990,8 @@ int main(int argc, char** argv)
     while (!is_quit)
     {
         static int onesec_tic = 0;
-        if (SDL_PollEvent(&event))
+        while (SDL_PollEvent(&event))
+	    {
             switch(event.type)
             {
                 case SDL_QUIT:
@@ -1084,6 +1085,7 @@ int main(int argc, char** argv)
                     keyboard_input(event.key.state == SDL_PRESSED, xtkey);
                 }
             }
+	    }
         if (mouse_capture && keyboard_ismsexit())
         {
             plat_mouse_capture(0);