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.