Correct unused-parameter warnings

[benrubson]

Hi,

This helps solving #426.

It solves following warnings :

In file included from DirNode.cpp:21:0:
DirNode.h:49:7: warning: unused parameter ‘src’ [-Wunused-parameter]
 class DirTraverse {
       ^
DirNode.cpp:58:52: note: synthesized method ‘encfs::DirTraverse::DirTraverse(const encfs::DirTraverse&)’ first required here 
 DirTraverse::DirTraverse(const DirTraverse &src) = default;
                                                    ^

In file included from Interface.cpp:21:0:
Interface.h:30:7: warning: unused parameter ‘src’ [-Wunused-parameter]
 class Interface {
       ^
Interface.cpp:41:7: note: synthesized method ‘encfs::Interface::Interface(const encfs::Interface&)’ first required here 
     = default;
       ^

Thx 👍

Ben