Add new wxCommandLinkButton class.

A command link button wraps a native MSW control under recent Windows versions
and is implemented generically as a simple bitmap button elsewhere.

In the future, GTK implementation should allow using a different font for the
button label and its note.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65327 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -411,6 +411,7 @@ MSW:
 
 All (GUI):
 
+- Added wxCommandLinkButton (Rickard Westerlund, GSoC 2010 project).
 - wxAUI: support auto-orientable toolbars (wsu).
 - Added wxDataViewCtrl::Set/GetCurrentItem().
 - wxHTML: render in RTL order inside RTL window (Richard Bullington-McGuire).