Use "wb" when writing binary STL exports, fixes #556.

code/STLExporter.cpp

@@ -75,7 +75,7 @@ void ExportSceneSTLBinary(const char* pFile,IOSystem* pIOSystem, const aiScene*
 	STLExporter exporter(pFile, pScene, true);
 
 	// we're still here - export successfully completed. Write the file.
-	boost::scoped_ptr<IOStream> outfile (pIOSystem->Open(pFile,"wt"));
+	boost::scoped_ptr<IOStream> outfile (pIOSystem->Open(pFile,"wb"));
 	if(outfile == NULL) {
 		throw DeadlyExportError("could not open output .stl file: " + std::string(pFile));
 	}