Restored the S2DGE

Considering the i686 fixes makes it function properly

src/include/86box/machine.h

@@ -78,6 +78,7 @@ enum {
     MACHINE_TYPE_SOCKET8,
     MACHINE_TYPE_SLOT1,
     MACHINE_TYPE_SLOT2,
+    MACHINE_TYPE_SLOT12,
     MACHINE_TYPE_SOCKET370,
     MACHINE_TYPE_MAX
 };
@@ -389,6 +390,7 @@ extern const device_t 	*at_tsunamiatx_get_device(void);
 
 /* m_at_slot2.c */
 extern int	machine_at_6gxu_init(const machine_t *);
+extern int	machine_at_s2dge_init(const machine_t *);
 
 /* m_at_socket370.c */
 extern int	machine_at_s370slm_init(const machine_t *);