Modified FGSubsystem::update() to take an int parameter for delta time

(i.e. multiloop).  Most subsystems currently ignore the parameter, but
eventually, it will allow all subsystems to update by time rather than
by framerate.

src/Main/viewer.cxx

@@ -57,3 +57,51 @@ void FGViewer::update() {
 // Destructor
 FGViewer::~FGViewer( void ) {
 }
+
+void
+FGViewer::init ()
+{
+}
+
+void
+FGViewer::bind ()
+{
+}
+
+void
+FGViewer::unbind ()
+{
+}
+
+void
+FGViewer::update (int dt)
+{
+  for ( int i = 0; i < dt; i++ ) {
+    if ( fabs(get_goal_view_offset() - get_view_offset()) < 0.05 ) {
+      set_view_offset( get_goal_view_offset() );
+      break;
+    } else {
+      // move current_view.view_offset towards
+      // current_view.goal_view_offset
+      if ( get_goal_view_offset() > get_view_offset() )
+	{
+	  if ( get_goal_view_offset() - get_view_offset() < SGD_PI ){
+	    inc_view_offset( 0.01 );
+	  } else {
+	    inc_view_offset( -0.01 );
+	  }
+	} else {
+	  if ( get_view_offset() - get_goal_view_offset() < SGD_PI ){
+	    inc_view_offset( -0.01 );
+	  } else {
+	    inc_view_offset( 0.01 );
+	  }
+	}
+      if ( get_view_offset() > SGD_2PI ) {
+	inc_view_offset( -SGD_2PI );
+      } else if ( get_view_offset() < 0 ) {
+	inc_view_offset( SGD_2PI );
+      }
+    }
+  }
+}

src/Main/viewer.hxx

@@ -34,6 +34,8 @@
 
 #include <plib/sg.h>		// plib include
 
+#include "fgfs.hxx"
+
 
 #define FG_FOV_MIN 0.1
 #define FG_FOV_MAX 179.9
@@ -129,6 +131,11 @@ public:
     // Destructor
     virtual ~FGViewer( void );
 
+    virtual void init ();
+    virtual void bind ();
+    virtual void unbind ();
+    virtual void update (int dt);
+
     //////////////////////////////////////////////////////////////////////
     // setter functions
     //////////////////////////////////////////////////////////////////////

src/Main/viewer_rph.hxx

@@ -69,7 +69,7 @@ public:
     ~FGViewerRPH( void );
 
     // Initialize a view class
-    void init( void );
+//      void init( void );
 
     //////////////////////////////////////////////////////////////////////
     // setter functions