Fix namespaces.

code/AssetLib/AC/ACLoader.cpp

@@ -60,7 +60,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <assimp/Importer.hpp>
 #include <memory>
 
-using namespace Assimp;
+namespace Assimp {
 
 static constexpr aiImporterDesc desc = {
     "AC3D Importer",
@@ -862,4 +862,6 @@ void AC3DImporter::InternReadFile(const std::string &pFile,
     }
 }
 
+} // namespace Assimp
+
 #endif //!defined ASSIMP_BUILD_NO_AC_IMPORTER