SCP: Add support for library unit test routines

sim_tape.c

@@ -88,6 +88,8 @@
    sim_tape_show_dens   show tape density
    sim_tape_set_async   enable asynchronous operation
    sim_tape_clr_async   disable asynchronous operation
+   aim_tape_test        unit test routine
+
 */
 
 #include "sim_defs.h"
@@ -2747,3 +2749,8 @@ else {                                                  /* otherwise get the den
 
 return SCPE_OK;
 }
+
+t_stat sim_tape_test (DEVICE *dptr)
+{
+return SCPE_OK;
+}