SITL: added SIM_SPEEDUP parameter

allows changing speed of simulation while running

libraries/SITL/SIM_Aircraft.cpp

@@ -360,6 +360,11 @@ void Aircraft::fill_fdm(struct sitl_fdm &fdm)
         fdm.longitude = smoothing.location.lng * 1.0e-7;
         fdm.altitude  = smoothing.location.alt * 1.0e-2;
     }
+
+    if (last_speedup != sitl->speedup && sitl->speedup > 0) {
+        set_speedup(sitl->speedup);
+        last_speedup = sitl->speedup;
+    }
 }
 
 uint64_t Aircraft::get_wall_time_us() const

libraries/SITL/SIM_Aircraft.h

@@ -147,6 +147,7 @@ protected:
     const char *autotest_dir;
     const char *frame;
     bool use_time_sync = true;
+    float last_speedup = -1;
 
     enum {
         GROUND_BEHAVIOR_NONE=0,

libraries/SITL/SITL.cpp

@@ -83,6 +83,7 @@ const AP_Param::GroupInfo SITL::var_info[] = {
     AP_GROUPINFO("MAG_ALY_HGT",   49, SITL,  mag_anomaly_hgt, 1.0f),
     AP_GROUPINFO("PIN_MASK",      50, SITL,  pin_mask, 0),
     AP_GROUPINFO("ADSB_TX",       51, SITL,  adsb_tx, 0),
+    AP_GROUPINFO("SPEEDUP",       52, SITL,  speedup, -1),
     AP_GROUPEND
 };
 

libraries/SITL/SITL.h

@@ -104,6 +104,7 @@ public:
     AP_Int8  flow_delay; // optflow data delay
     AP_Int8  terrain_enable; // enable using terrain for height
     AP_Int8  pin_mask; // for GPIO emulation
+    AP_Float speedup; // simulation speedup
 
     // wind control
     float wind_speed_active;