Bug fix - cdrom media emulation only moves drives if of the same type.

The bug caused floppies to move when hard drive emulation was in
    effect, and vice-versa.  This patch fixes it.
diff --git a/src/disk.c b/src/disk.c
index dfaa24f..9bad1d7 100644
--- a/src/disk.c
+++ b/src/disk.c
@@ -697,11 +697,12 @@
         }
         u16 ebda_seg = get_ebda_seg();
         if (GET_EBDA2(ebda_seg, cdemu.active)) {
-            if (drive == GET_EBDA2(ebda_seg, cdemu.emulated_drive)) {
+            u8 emudrive = GET_EBDA2(ebda_seg, cdemu.emulated_drive);
+            if (drive == emudrive) {
                 cdemu_13(regs);
                 return;
             }
-            if (drive < 0xe0)
+            if (drive < 0xe0 && ((emudrive ^ drive) & 0x80) == 0)
                 drive--;
         }
     }