Add a new class allowing to store passwords and other sensitive information
using the OS-provided facilities.
Add implementations for all the main platforms, documentation and a new sample
(which contains an ad hoc unit test as the real unit test for this class would
probably be a bad idea as it wouldn't run in non-interactive contexts and
could show OS level dialog boxes if it did).
This keyword is not expanded by Git which means it's not replaced with the
correct revision value in the releases made using git-based scripts and it's
confusing to have lines with unexpanded "$Id$" in the released files. As
expanding them with Git is not that simple (it could be done with git archive
and export-subst attribute) and there are not many benefits in having them in
the first place, just remove all these lines.
If nothing else, this will make an eventual transition to Git simpler.
Closes#14487.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74602 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
