* Move from deprecated wxScopedPtr to std::unique_ptr
wxScopedPtr was included previously through some header hierarchy which as of 3.3 is
no longer the case causing it to break. But instead of including a header for a deprecated
function explicitly, just move to std::unique_ptr as recommended by upstream.
* Convert to explicit conversions from wxString
As of https://github.com/wxWidgets/wxWidgets/pull/23449/commits/35c35c235e9c29b40002131602e050dca8d65b8c
wxWidgets defaults to STL classes, which has a side-effect that
some implicit conversions break. This patch converts those conversions
to explicit in anticipation of wxWidgets 3.3 release.