Add "inherit" to <font> XRC tag.

This allows to construct a font based on the parent window font instead of
either fully specifying all font parameters or basing it on a standard font.

Closes #14632.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72572 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/xrc/xmlres.h

@@ -594,7 +594,7 @@ protected:
 #endif
 
     // Gets a font.
-    wxFont GetFont(const wxString& param = wxT("font"));
+    wxFont GetFont(const wxString& param = wxT("font"), wxWindow* parent = NULL);
 
     // Gets the value of a boolean attribute (only "0" and "1" are valid values)
     bool GetBoolAttr(const wxString& attr, bool defaultv);