AP_Math: added is_nan() methods to vector3f and matrix3f

libraries/AP_Math/matrix3.h

@@ -124,6 +124,10 @@ public:
 	Matrix3<T> transpose(void)
 	{	return *this = transposed();	}
 
+	// check if any elements are NAN
+	bool is_nan(void)
+		{   return a.is_nan() || b.is_nan() || c.is_nan(); }
+
 };
 
 typedef Matrix3<int16_t>		Matrix3i;

libraries/AP_Math/vector3.h

@@ -173,6 +173,10 @@ public:
 	T angle_normalized(const Vector3<T> &v1, const Vector3<T> &v2)
 	{   return (T)acosf(v1*v2);  }
 
+	// check if any elements are NAN
+	bool is_nan(void)
+		{   return isnan(x) || isnan(y) || isnan(z); }
+
 };
 
 typedef Vector3<int16_t>		Vector3i;