fix "headercheck":

part of https://github.com/assimp/assimp/issues/534

code/FileSystemFilter.h

@@ -46,8 +46,10 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define AI_FILESYSTEMFILTER_H_INC
 
 #include "../include/assimp/IOSystem.hpp"
+#include "../include/assimp/DefaultLogger.hpp"
 #include "fast_atof.h"
 #include "ParsingUtils.h"
+
 namespace Assimp	{
 
 inline bool IsHex(char s) {