Support C++17

C++17 removes std::bind2nd from the std library. It's easy to replace the two instances of it in src/MeshEditor.cc.

Original code:
`replace_if(mNodeMask.begin(), mNodeMask.end(), bind2nd(equal_to(), 2), 1);`

New code:
`replace_if(mNodeMask.begin(), mNodeMask.end(), [] (unsigned val) { return val == 2; }, 1);`

Open src/MeshEditor.cc and locate the two uses of std::bind2nd described in the issue. Replace them with the shown C++17-compatible lambda form, then build the project with C++17 enabled. Done means both instances are updated and the project builds successfully without std::bind2nd.

Written by the indexing model from the issue text.