Don't include cpu.h in timer.h

Change the name of the define used to indicate SVGA multi-monitor-capable cards

src/include/86box/timer.h

@@ -1,7 +1,7 @@
 #ifndef _TIMER_H_
 #define _TIMER_H_
 
-#include "cpu.h"
+extern uint64_t tsc;
 
 /* Maximum period, currently 1 second. */
 #define MAX_USEC64    1000000ULL

src/include/86box/video.h

@@ -69,6 +69,8 @@ enum {
 #define VIDEO_FLAG_TYPE_NONE    5
 #define VIDEO_FLAG_TYPE_MASK    7
 
+#define VIDEO_FLAG_TYPE_SECONDARY VIDEO_FLAG_TYPE_SPECIAL
+
 typedef struct video_timings_t {
     int type;
     int write_b;