Applied patch [ 1174270 ] small fixes to wxGenericDirCtrl

Applied patch [ 1174270 ] small fixes to wxGenericDirCtrl
Stas Sergeev:

1. CollapseDir() was forgetting to... hrmm, to collapse
the dir...
It was only removing the child elements, leaving the dir
expanded. Missing code added.

2. ReCreateTree(), which, according to the comments, must
collapse and re-open the tree, was not re-opening it.
Fixed.

3. For those who used the bogus ReCreateTree() behaviour
to collapse the tree, I added CollapseTree(). This does
visually what the ReCreateTree() wrongly did before the
patch.

4. Documentation is updated accordingly.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@33223 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775