Merge pull request #1814 from assimp/cppcheck_fixes

fix cppcheck findings.

code/3DSExporter.cpp

@@ -184,7 +184,7 @@ void ExportScene3DS(const char* pFile, IOSystem* pIOSystem, const aiScene* pScen
 } // end of namespace Assimp
 
 // ------------------------------------------------------------------------------------------------
-Discreet3DSExporter:: Discreet3DSExporter(std::shared_ptr<IOStream> outfile, const aiScene* scene)
+Discreet3DSExporter:: Discreet3DSExporter(std::shared_ptr<IOStream> &outfile, const aiScene* scene)
 : scene(scene)
 , writer(outfile)
 {

code/3DSExporter.h

@@ -67,7 +67,7 @@ namespace Assimp
 // ------------------------------------------------------------------------------------------------
 class Discreet3DSExporter {
 public:
-    Discreet3DSExporter(std::shared_ptr<IOStream> outfile, const aiScene* pScene);
+    Discreet3DSExporter(std::shared_ptr<IOStream> &outfile, const aiScene* pScene);
     ~Discreet3DSExporter();
 
 private: