AP_Logger: Log GPS yaw accuracy

libraries/AP_Logger/LogFile.cpp

@@ -173,6 +173,7 @@ void AP_Logger::Write_GPS(uint8_t i, uint64_t time_us)
         hacc          : (uint16_t)MIN((hacc*100), UINT16_MAX),
         vacc          : (uint16_t)MIN((vacc*100), UINT16_MAX),
         sacc          : (uint16_t)MIN((sacc*100), UINT16_MAX),
+        yaw_accuracy  : yaw_accuracy_deg,
         have_vv       : (uint8_t)gps.have_vertical_velocity(i),
         sample_ms     : gps.last_message_time_ms(i),
         delta_ms      : gps.last_message_delta_time_ms(i)

libraries/AP_Logger/LogStructure.h

@@ -223,6 +223,7 @@ struct PACKED log_GPA {
     uint16_t hacc;
     uint16_t vacc;
     uint16_t sacc;
+    float    yaw_accuracy;
     uint8_t  have_vv;
     uint32_t sample_ms;
     uint16_t delta_ms;
@@ -1223,10 +1224,10 @@ struct PACKED log_Arm_Disarm {
 #define ESC_UNITS "sqvAO-"
 #define ESC_MULTS "FBBBB-"
 
-#define GPA_LABELS "TimeUS,VDop,HAcc,VAcc,SAcc,VV,SMS,Delta"
-#define GPA_FMT   "QCCCCBIH"
-#define GPA_UNITS "smmmn-ss"
-#define GPA_MULTS "FBBBB-CC"
+#define GPA_LABELS "TimeUS,VDop,HAcc,VAcc,SAcc,YAcc,VV,SMS,Delta"
+#define GPA_FMT   "QCCCCfBIH"
+#define GPA_UNITS "smmmnd-ss"
+#define GPA_MULTS "FBBBB0-CC"
 
 // see "struct GPS_State" and "Write_GPS":
 #define GPS_LABELS "TimeUS,Status,GMS,GWk,NSats,HDop,Lat,Lng,Alt,Spd,GCrs,VZ,Yaw,U"