Fix unused private vars.

Xcode is warning about these, they're a mixture of
copy-pasted code, evolved use (e.g. using a property
node to store state), and so on.

src/AIModel/AIEscort.hxx

@@ -76,11 +76,9 @@ private:
     SGGeod _tgtpos;
 
     bool   _solid;           // if true ground is solid for FDMs
-    double _load_resistance; // ground load resistanc N/m^2
-    double _frictionFactor;  // dimensionless modifier for Coefficient of Friction
     double _tgtrange, _tgtbrg;
     double _ht_agl_ft;
-    double _relbrg, _truebrg;
+    double _relbrg;
     double _parent_speed, _parent_hdg;
     double _interval;
 

src/AIModel/AIManager.hxx

@@ -122,7 +122,6 @@ private:
     double user_yaw;
     double user_roll;
     double user_speed;
-    double user_agl;
     double wind_from_east;
     double wind_from_north;
 

src/Environment/atmosphere.cxx

@@ -223,7 +223,7 @@ void FGAtmoCache::check_model() {
 
 //////////////////////////////////////////////////////////////////////
 
-FGAltimeter::FGAltimeter() : kset(atmodel::ISA::P0), kft(0)
+FGAltimeter::FGAltimeter()
 {
     cache();
 }

src/Environment/atmosphere.hxx

@@ -136,9 +136,6 @@ public:
 
 
 class FGAltimeter : public FGAtmoCache {
-    double kset;
-    double kft;
-
 public:
     FGAltimeter();
     double reading_ft(const double p_inHg,

src/Input/FGMacOSXEventInput.cxx

@@ -343,7 +343,7 @@ void HIDElement::generateEvent(FGMacOSXInputDevice *device, double dt, int modif
 }
 
 AxisElement::AxisElement(CFDictionaryRef element, long page, long usage) : 
-  HIDElement(element, page, usage), dead_band(0.00), saturate(1.0)
+  HIDElement(element, page, usage), dead_band(0.00)
 {
   min = GetHIDElementLongValue(element, kIOHIDElementMinKey); 
   max = GetHIDElementLongValue(element, kIOHIDElementMaxKey);

src/Input/FGMacOSXEventInput.hxx

@@ -119,7 +119,6 @@ private:
   long min;
   long max;
   float dead_band;
-  float saturate;
   long center;
   bool isRelative;
   bool isWrapping;

src/Instrumentation/HUD/HUD_private.hxx

@@ -181,9 +181,7 @@ private:
     Format  _mode;
     std::string  _format;
     int     _halign;    // HUDText alignment
-    int     _blink;
     bool    _box;
-    float   _text_y;
     float   _pointer_width;
     float   _pointer_length;
 

src/Instrumentation/slip_skid_ball.hxx

@@ -41,9 +41,6 @@ public:
     virtual void update (double dt);
 
 private:
-
-    double _last_pos;
-
     std::string _name;
     int _num;
 

src/Instrumentation/tacan.hxx

@@ -93,14 +93,12 @@ private:
     SGVec3d _transmitter;
     SGGeod _transmitter_pos;
     double _transmitter_range_nm;
-    double _transmitter_bearing_deg;
     double _transmitter_bias;
     std::string _transmitter_name;
     std::string _transmitter_ident;
 
     SGGeod _mobilePos;
     double _mobile_range_nm;
-    double _mobile_bearing_deg;
     double _mobile_bias;
     std::string _mobile_name;
     std::string _mobile_ident;

src/Instrumentation/tcas.cxx

@@ -112,11 +112,6 @@ using std::string;
 #  include <Include/no_version.h>
 #endif
 
-#include <Main/fg_props.hxx>
-#include <Main/globals.hxx>
-#include "instrument_mgr.hxx"
-#include "tcas.hxx"
-
 ///////////////////////////////////////////////////////////////////////////////
 // debug switches /////////////////////////////////////////////////////////////
 ///////////////////////////////////////////////////////////////////////////////
@@ -127,6 +122,11 @@ using std::string;
 //#define FEATURE_TCAS_DEBUG_ADV_GENERATOR
 //#define FEATURE_TCAS_DEBUG_PROPERTIES
 
+#include <Main/fg_props.hxx>
+#include <Main/globals.hxx>
+#include "instrument_mgr.hxx"
+#include "tcas.hxx"
+
 ///////////////////////////////////////////////////////////////////////////////
 // constants //////////////////////////////////////////////////////////////////
 ///////////////////////////////////////////////////////////////////////////////
@@ -532,9 +532,11 @@ TCAS::AdvisoryCoordinator::update(int mode)
 
 TCAS::ThreatDetector::ThreatDetector(TCAS* _tcas) :
     tcas(_tcas),
-    checkCount(0),
     pAlarmThresholds(&sensitivityLevels[0])
 {
+#ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
+    checkCount = 0;
+#endif
     self.radarAltFt = 0.0;
     unitTest();
 }

src/Instrumentation/tcas.hxx

@@ -342,7 +342,9 @@ class TCAS : public SGSubsystem
         static const SensitivityLevel sensitivityLevels[];
 
         TCAS*              tcas;
+#ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
         int                checkCount;
+#endif // of FEATURE_TCAS_DEBUG_THREAT_DETECTOR
         
         SGPropertyNode_ptr nodeLat;
         SGPropertyNode_ptr nodeLon;