Document that wxTreeCtrl::DeleteChildren() does send events

Contrary to what the documentation stated previously, this function does
generate the wxEVT_TREE_DELETE_ITEM events for all the items being
deleted, in both MSW and generic implementations.

Update the documentation and add a new unit test checking that the
behaviour really conforms to it.

interface/wx/treectrl.h

@@ -317,8 +317,10 @@ public:
     virtual void DeleteAllItems();
 
     /**
-        Deletes all children of the given item (but not the item itself). Note
+        Deletes all children of the given item (but not the item itself).
-        that this will @b not generate any events unlike Delete() method.
+
+        A @c wxEVT_TREE_DELETE_ITEM event will be generated for every item
+        being deleted.
 
         If you have called SetItemHasChildren(), you may need to call it again
         since DeleteChildren() does not automatically clear the setting.

tests/controls/treectrltest.cpp

@@ -45,6 +45,7 @@ private:
     CPPUNIT_TEST_SUITE( TreeCtrlTestCase );
         WXUISIM_TEST( ItemClick );
         CPPUNIT_TEST( DeleteItem );
+        CPPUNIT_TEST( DeleteChildren );
         WXUISIM_TEST( LabelEdit );
         WXUISIM_TEST( KeyDown );
 #ifndef __WXGTK__
@@ -72,6 +73,7 @@ private:
 
     void ItemClick();
     void DeleteItem();
+    void DeleteChildren();
     void LabelEdit();
     void KeyDown();
 #ifndef __WXGTK__
@@ -275,6 +277,16 @@ void TreeCtrlTestCase::DeleteItem()
     CPPUNIT_ASSERT_EQUAL(1, deleteitem.GetCount());
 }
 
+void TreeCtrlTestCase::DeleteChildren()
+{
+    EventCounter deletechildren(m_tree, wxEVT_TREE_DELETE_ITEM);
+
+    m_tree->AppendItem(m_child1, "another grandchild");
+    m_tree->DeleteChildren(m_child1);
+
+    CHECK( deletechildren.GetCount() == 2 );
+}
+
 #if wxUSE_UIACTIONSIMULATOR
 
 void TreeCtrlTestCase::LabelEdit()