Fixed include: IFCReaderGen_4 instead of IFCReaderGen4

code/Importer/IFC/IFCReaderGen_4.cpp

@@ -43,7 +43,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef ASSIMP_BUILD_NO_IFC_IMPORTER
 
 #include "AssimpPCH.h"
-#include "IFCReaderGen4.h"
+#include "IFCReaderGen_4.h"
 
 namespace Assimp {
 using namespace IFC;