minor updates to GTK-specific comments

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75069 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
spelling fixes

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75070 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775