Recast: add missing mset version directive

Not for MSET < 7.

src/thirdparty/recast/Detour/Include/DetourNavMesh.h

@@ -229,12 +229,14 @@ struct dtPoly
 	/// The poly surface area. (Quantized by #DT_POLY_AREA_QUANT_FACTOR).
 	unsigned short surfaceArea;
 
+#if DT_NAVMESH_SET_VERSION >= 7
 	// These 2 are most likely related, it needs to be reversed still.
 	// No use case has been found in the executable yet, its possible these are
 	// used internally in the editor. Dynamic reverse engineering required to
 	// confirm this.
 	unsigned short unk1;
 	unsigned short unk2;
+#endif
 
 	/// The center of the polygon; see abstracted script function 'Navmesh_RandomPositions'.
 	float center[3];

src/thirdparty/recast/Detour/Source/DetourNavMeshBuilder.cpp

@@ -296,10 +296,12 @@ bool dtCreateDisjointPolyGroups(dtNavMesh* nav, dtDisjointSet& disjoint)
 			dtPoly& poly = tile->polys[j];
 			poly.groupId = DT_NULL_POLY_GROUP;
 
+#if DT_NAVMESH_SET_VERSION >= 7
 			// NOTE: these fields are unknown and need to be reversed.
 			// It is possible these are used internally only.
 			poly.unk1 = (unsigned short)-1;
 			poly.unk2 = (unsigned short)-1;
+#endif
 		}
 	}