Make wxCOL_WIDTH_AUTOSIZE work dynamically in generic wxDataViewCtrl

Caching the best column widths broke autosizing behaviour if the column title
was updated after setting the width to wxCOL_WIDTH_AUTOSIZE.

Fix this by invaliding the column cached width if its text changes.

src/generic/datavgen.cpp

@@ -186,6 +186,15 @@ void wxDataViewColumn::UpdateDisplay()
     }
 }
 
+void wxDataViewColumn::UpdateWidth()
+{
+    if (m_owner)
+    {
+        int idx = m_owner->GetColumnIndex( this );
+        m_owner->OnColumnWidthChange( idx );
+    }
+}
+
 void wxDataViewColumn::UnsetAsSortKey()
 {
     m_sort = false;
@@ -4846,6 +4855,13 @@ bool wxDataViewCtrl::InsertColumn( unsigned int pos, wxDataViewColumn *col )
     return true;
 }
 
+void wxDataViewCtrl::OnColumnWidthChange(unsigned int idx)
+{
+    InvalidateColBestWidth(idx);
+
+    OnColumnChange(idx);
+}
+
 void wxDataViewCtrl::OnColumnChange(unsigned int idx)
 {
     if ( m_headerArea )