MSYS build scripts and instructions (#99) and warning fixes

* Preliminary MSYS2 + MinGW build scripts and instructions.

* CMakeLists.txt: MinGW tweaks, enforce C++03, suppress warnings for now.

* Fix some GCC warnings.

* Fix unused parameter warnings coming from Ifc*.h.

* Fix warning regarding unreachable code (++jt) on MSVC.

* Add IfcParse_EXPORT for IfcInvalidTokenException

* Fix potentially uninitialized pointer variables.

* Note about OpenCASCADE cyclic dependencies fix.

* GCC warning fix: don't generate 'current_enum' variable that is only set and not used for anything ever

* Work around -Wmaybe-uninitialized warnings about boost::optional constructs. Also prevent passing of negative values for --bounds.

* Remove unused variable.

* CMakeLists.txt: ENABLE_BUILD_OPTIMIZATIONS for GCC (simply enforce -03)

src/ifcgeom/IfcGeom.h

@@ -280,9 +280,9 @@ public:
 			return _get_surface_style<T>(representation_item->as<IfcSchema::IfcStyledItem>());
 		}
 		IfcSchema::IfcStyledItem::list::ptr styled_items = representation_item->StyledByItem();
-		for (IfcSchema::IfcStyledItem::list::it jt = styled_items->begin(); jt != styled_items->end(); ++jt) {
+		if (styled_items->size()) {
 			// StyledByItem is a SET [0:1] OF IfcStyledItem, so we return after the first IfcStyledItem:
-			return _get_surface_style<T>(*jt);
+			return _get_surface_style<T>(*styled_items->begin());
 		}
 		return std::make_pair<IfcSchema::IfcSurfaceStyle*, T*>(0,0);
 	}

src/ifcgeom/IfcGeomFunctions.cpp

@@ -1366,7 +1366,6 @@ bool IfcGeom::Kernel::convert_layerset(const IfcSchema::IfcProduct* product, std
 	const IfcSchema::IfcMaterialLayerSet* layerset = usage->ForLayerSet();
 	const bool positive = usage->DirectionSense() == IfcSchema::IfcDirectionSenseEnum::IfcDirectionSense_POSITIVE;
 	double offset = usage->OffsetFromReferenceLine() * getValue(GV_LENGTH_UNIT);
-	const int axis = usage->LayerSetDirection();
 
 	IfcSchema::IfcMaterialLayer::list::ptr material_layers = layerset->MaterialLayers();
 
@@ -1723,7 +1722,7 @@ bool IfcGeom::Kernel::fold_layers(const IfcSchema::IfcWall* wall, const IfcRepre
 
 			bool found_intersection = false;
 			boost::optional<gp_Pnt> point_outside_param_range;
-			double param;
+			//double param;
 				
 			const Handle_Geom_Surface& surface = *jt;
 
@@ -1734,7 +1733,7 @@ bool IfcGeom::Kernel::fold_layers(const IfcSchema::IfcWall* wall, const IfcRepre
 				intersections.Parameters(1, u, v, w);
 				if (w < axis_u1 || w > axis_u2) {
 					point_outside_param_range = p;
-					param = w;
+					//param = w;
 				} else {
 					// Found an intersection. Layer end point is covered by connecting wall
 					found_intersection = true;

src/ifcgeom/IfcGeomIterator.h

@@ -393,8 +393,6 @@ namespace IfcGeom {
 						}
 					}
 
-					const int repid = representation->entity->id();
-					
 					bool has_openings = false;
 					bool has_layers = false;
 

src/ifcgeom/IfcGeomSerialisation.cpp

@@ -43,6 +43,7 @@ int convert_to_ifc(const gp_Ax2& a, IfcSchema::IfcAxis2Placement3D*& ax, bool ad
 	IfcSchema::IfcCartesianPoint* p;
 	IfcSchema::IfcDirection *x, *z;
 	if (!(convert_to_ifc(a.Location(), p, advanced) && convert_to_ifc(a.Direction(), z, advanced) && convert_to_ifc(a.XDirection(), x, advanced))) {
+        ax = 0;
 		return 0;
 	}
 	ax = new IfcSchema::IfcAxis2Placement3D(p, z, x);

src/ifcgeom/IfcGeomShapes.cpp

@@ -1150,7 +1150,6 @@ bool IfcGeom::Kernel::convert(const IfcSchema::IfcTriangulatedFaceSet* l, TopoDS
 
 	if (faces.empty()) return false;
 	
-	const unsigned int num_faces = (unsigned)indices.size();
 	bool valid_shell = false;
 
 	if (faces.size() < getValue(GV_MAX_FACES_TO_SEW)) {