Remove transitive include for Detour (#1450)

Moves it to the 1 cpp file that uses it and locks down its header.

Still compiles and links.

dNavigation/dNavMesh.h

@@ -2,13 +2,17 @@
 
 #include <cstdint>
 #include <vector>
-#include <map>
-#include <string>
-#include <cstring>
-
-#include "DetourExtensions.h"
 
 class NiPoint3;
+class rcHeightfield;
+class rcCompactHeightfield;
+class rcContourSet;
+class rcPolyMesh;
+class rcPolyMeshDetail;
+class InputGeom;
+class dtNavMesh;
+class dtNavMeshQuery;
+class rcContext;
 
 class dNavMesh {
 public:
@@ -26,24 +30,14 @@ public:
 	float GetHeightAtPoint(const NiPoint3& location, const float halfExtentsHeight = 32.0f) const;
 	std::vector<NiPoint3> GetPath(const NiPoint3& startPos, const NiPoint3& endPos, float speed = 10.0f);
 
-	class dtNavMesh* GetdtNavMesh() { return m_NavMesh; }
+	bool IsNavmeshLoaded() { return m_NavMesh != nullptr; }
 
 private:
 	void LoadNavmesh();
 
 	uint32_t m_ZoneId;
 
-	uint8_t* m_Triareas = nullptr;
-	rcHeightfield* m_Solid = nullptr;
-	rcCompactHeightfield* m_CHF = nullptr;
-	rcContourSet* m_CSet = nullptr;
-	rcPolyMesh* m_PMesh = nullptr;
-	rcConfig m_Config;
-	rcPolyMeshDetail* m_PMDMesh = nullptr;
-
-	class InputGeom* m_Geometry = nullptr;
-	class dtNavMesh* m_NavMesh = nullptr;
-	class dtNavMeshQuery* m_NavQuery = nullptr;
+	dtNavMesh* m_NavMesh = nullptr;
+	dtNavMeshQuery* m_NavQuery = nullptr;
 	uint8_t m_NavMeshDrawFlags;
-	rcContext* m_Ctx = nullptr;
 };