Completely reworked mouse handling - should now be smoother due to there no longer being a multi-layered game of telephone going on with all the various interim coordinate counters, also rewritten the serial mouse emulation ground ground up.

src/86box.c

@@ -1279,10 +1279,12 @@ pc_run(void)
     startblit();
     cpu_exec(cpu_s->rspeed / 100);
 #ifdef USE_GDBSTUB /* avoid a KBC FIFO overflow when CPU emulation is stalled */
-    // if (gdbstub_step == GDBSTUB_EXEC)
+    if (gdbstub_step == GDBSTUB_EXEC) {
 #endif
-#if 0
-        mouse_process();
+        if (!mouse_timed)
+            mouse_process();
+#ifdef USE_GDBSTUB /* avoid a KBC FIFO overflow when CPU emulation is stalled */
+    }
 #endif
     joystick_process();
     endblit();