Fix the alignment used by custom wxDVC renderers in wxGTK by default.

Correctly initialize the alignment used by the text renderer used by
wxDataViewCustomRenderer in wxGTK implementation of wxDataViewCtrl.

Closes #12298.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68323 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/dvrenderers.h

@@ -147,6 +147,10 @@ protected:
     bool Init(wxDataViewCellMode mode, int align);
 
 private:
+    // Called from GtkGetTextRenderer() to really create the renderer if
+    // necessary.
+    void GtkInitTextRenderer();
+
     wxDC        *m_dc;
 
     GtkCellRendererText      *m_text_renderer;