fix namespace issue in fuzzer.

fuzz/assimp_fuzzer.cc

@@ -42,6 +42,8 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <assimp/scene.h>
 #include <assimp/postprocess.h>
 
+using namespace Assimp;
+
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t dataSize) {
 	aiLogStream stream = aiGetPredefinedLogStream(aiDefaultLogStream_STDOUT,NULL);
 	aiAttachLogStream(&stream);