Block in wxMSW wxProgressDialog::Update(max) until the dialog is dismissed.

Block in wxMSW wxProgressDialog::Update(max) until the dialog is dismissed.

For consistency with the generic version and because it makes more sense than
blocking in the dialog destructor (which is the only other alternative for the
dialogs without wxPD_AUTO_HIDE to work), we should block in Update() when the
maximal value is reached for dialogs without wxPD_AUTO_HIDE style until the
dialog is dismissed.

Document this behaviour even more clearly.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65507 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775