Use Cocoa methods instead of wx ones in wxDVC font setting code.

Use Cocoa methods instead of wx ones in wxDVC font setting code.

Use NSFontManager to create bold or italic version of the font instead of
using wxFont. This works better for the bold attribute, but setting the italic
one still doesn't do anything.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62388 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775