Fix wxNativeFontInfo::InitFromFont() when using Pango

Use pango_font_description_copy() to make a lossless copy of the original font
instead of doing it using wxWidgets API which is less direct and, in addition,
currently is completely broken as SetXXX() methods don't create the Pango font
description if it doesn't exist as they ought to.

Closes https://github.com/wxWidgets/wxWidgets/pull/312

include/wx/fontutil.h

@@ -230,6 +230,9 @@ public:
     // init with the parameters of the given font
     void InitFromFont(const wxFont& font)
     {
+#if wxUSE_PANGO
+        Init(*font.GetNativeFontInfo());
+#else
         // translate all font parameters
         SetStyle((wxFontStyle)font.GetStyle());
         SetWeight((wxFontWeight)font.GetWeight());
@@ -255,6 +258,7 @@ public:
         // deal with encoding now (it may override the font family and facename
         // so do it after setting them)
         SetEncoding(font.GetEncoding());
+#endif // !wxUSE_PANGO
     }
 
     // accessors and modifiers for the font elements