Not only simplifies the code but makes the application more
coherent with other Windows and Linux applications as the
recent documents lists is populated when you open the file.
Also, for Windows 7 and higher, it makes a call to
Application::AddToRecentDocumentList. Tested on Windows
and Linux.

Change-Id: I360acc9723260d5827eb83e3c240ab0673352af6
Reviewed-on: https://gerrit.libreoffice.org/5266Reviewed-by: Tor Lillqvist <tml@iki.fi>
Tested-by: Tor Lillqvist <tml@iki.fi>