Allow custom handling of Enter/Tab with modifiers in wxDataViewCtrl

While Enter and Tab on their own should be used to finish cell editing, the
cell editor itself may want to process key combinations involving these keys
with modifiers, e.g. Shift-Enter, so don't intercept those in at least the
generic version of wxDataViewCtrl to allow catching them in the editor.

src/common/datavcmn.cpp

@@ -1044,17 +1044,20 @@ void wxDataViewEditorCtrlEvtHandler::OnChar( wxKeyEvent &event )
 {
     switch ( event.m_keyCode )
     {
-        case WXK_RETURN:
-            m_finished = true;
-            m_owner->FinishEditing();
-            break;
-
         case WXK_ESCAPE:
-        {
             m_finished = true;
             m_owner->CancelEditing();
             break;
-        }
+
+        case WXK_RETURN:
+            if ( !event.HasAnyModifiers() )
+            {
+                m_finished = true;
+                m_owner->FinishEditing();
+                break;
+            }
+            wxFALLTHROUGH; // Ctrl/Alt/Shift-Enter is not handled specially
+
         default:
             event.Skip();
     }

src/generic/datavgen.cpp

@@ -3632,7 +3632,17 @@ void wxDataViewMainWindow::OnCharHook(wxKeyEvent& event)
                 return;
 
             case WXK_RETURN:
+                // Shift-Enter is not special neither.
+                if ( event.ShiftDown() )
+                    break;
+                wxFALLTHROUGH;
+
             case WXK_TAB:
+                // Ctrl/Alt-Tab or Enter could be used for something else, so
+                // don't handle them here.
+                if ( event.HasModifiers() )
+                    break;
+
                 m_editorRenderer->FinishEditing();
                 return;
         }