ArduCopter: reduce redundant event logging

We now only write state changes to the dataflash log when they have
changed.
Also replaced <tab> with <space> in AP_State.pde

ArduCopter/AP_State.pde

@@ -3,18 +3,26 @@
 
 void set_home_is_set(bool b)
 {
-    ap.home_is_set 	= b;
+    // if no change, exit immediately
+    if( ap.home_is_set == b )
+        return;
 
-	if(b) Log_Write_Event(DATA_SET_HOME);
+    ap.home_is_set 	= b;
+    if(b) {
+        Log_Write_Event(DATA_SET_HOME);
+    }
 }
 
 // ---------------------------------------------
 void set_armed(bool b)
 {
+    // if no change, exit immediately
+    if( ap.armed == b )
+        return;
+
     ap.armed = b;
     if(b){
         Log_Write_Event(DATA_ARMED);
-
     }else{
         Log_Write_Event(DATA_DISARMED);
     }
@@ -23,6 +31,10 @@ void set_armed(bool b)
 // ---------------------------------------------
 void set_auto_armed(bool b)
 {
+    // if no change, exit immediately
+    if( ap.auto_armed == b )
+        return;
+
     ap.auto_armed = b;
     if(b){
         Log_Write_Event(DATA_AUTO_ARMED);
@@ -38,9 +50,9 @@ void set_simple_mode(bool b)
         }else{
             Log_Write_Event(DATA_SET_SIMPLE_OFF);
         }
-	}
         ap.simple_mode = b;
     }
+}
 
 // ---------------------------------------------
 static void set_failsafe(bool mode)
@@ -75,6 +87,10 @@ void set_low_battery(bool b)
 // ---------------------------------------------
 void set_takeoff_complete(bool b)
 {
+    // if no change, exit immediately
+    if( ap.takeoff_complete == b )
+        return;
+
     if(b){
         Log_Write_Event(DATA_TAKEOFF);
     }
@@ -84,6 +100,10 @@ void set_takeoff_complete(bool b)
 // ---------------------------------------------
 void set_land_complete(bool b)
 {
+    // if no change, exit immediately
+    if( ap.land_complete == b )
+        return;
+
     if(b){
         Log_Write_Event(DATA_LAND_COMPLETE);
     }
@@ -136,5 +156,4 @@ void set_gps_healthy(bool b)
 void dump_state()
 {
     cliSerial->printf("st: %u\n",ap.value);
-	//cliSerial->printf("%u\n", *(uint16_t*)&ap);
 }