remove pre-build proto/grpc files (they differ for each platform and proto/grpc version)

examples/Importers/ImportMJCFDemo/BulletMJCFImporter.h

@@ -7,6 +7,7 @@
 
 struct MJCFErrorLogger
 {
+	virtual ~MJCFErrorLogger() {}
 	virtual void reportError(const char* error)=0;
 	virtual void reportWarning(const char* warning)=0;
 	virtual void printMessage(const char* msg)=0;