[REVIEW 3-6] fdo#53006: And detect LO downgrading scenarios

As Petr found out, if you first run LO 3.6.1, then some old LO 3.5.x 
(making use of share/prereg/bundled), then LO 3.6.1 again, all on the 
same UserInstallation, it can still happen that LO 3.6.1 refuses to 
start (as LO 3.5.x copied potentially broken data to 
user/extensions/bundled but did not touch 
user/extensions/bundled/buildid, so that LO 3.6.1 would not detect that 
it needs to remove the potentially poisonous data again).

<http://cgit.freedesktop.org/libreoffice/core/commit/?id=e9631f40ee49a244b6c6816e5cfb36814b9bafba> 
"fdo#53006: And detect LO downgrading scenarios..." addresses that by 
adding yet another pirouette (even though one could argue that such 
downgrading scenarios never worked by design, anyway).  Between Petr and 
me, we have seen it to be effective for both Linux and Windows (master, 
at least).  Please review and consider for backporting to libreoffice-3-6.

Thanks,
Stephan