Fix 'make check' after Gtk::Alignment has been deprecated

* examples/book/alignment/examplewindow.[h|cc]:
* examples/book/placessidebar/examplewindow.[h|cc]:
* examples/book/progressbar/examplewindow.[h|cc]: Use set_halign(),
set_margin_start() etc. instead of Alignment.
Mention that Arrow, Alignment and most Button signals are deprecated

* docs/tutorial/C/index-in.docbook