SCP: Fold up include files used by all simulators

- Add common system includes used in may places which are allowed
  and thus added directly in sim_defs.h.
- Separate completely private system data structures and system APIs
  for use only by SCP library routines into sim_scp_private.h.

sim_console.c

@@ -128,11 +128,10 @@
 */
 
 #include "sim_defs.h"
+#include "sim_scp_private.h"
 #include "sim_tmxr.h"
 #include "sim_serial.h"
 #include "sim_timer.h"
-#include <ctype.h>
-#include <math.h>
 
 #ifdef __HAIKU__
 #define nice(n) ({})