update keepassx to 2.0 series

In spite of the alpha version scheme, this is the most usable version
available, support for the previous release series was EOL'ed a long
while back and they are completely unmaintained (last patch release over
4 years ago). The 2.0 series was started 4 years ago and has been
releasing builds labeled alpha since May 2012. Anybody actually using
this software is using these builds in spite of the version labeling
scheme.
Merge pull request #3681 from alerque/patch-2

update keepassx to 2.0 series