Compilation fix for wxFont in wxGTK1.

wx/encinfo.h is not included from wx/wx.h so include it explicitly.

This is the same change as was done in r73519 for wxX11/wxMotif.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73890 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775