[mythtv] UIType aligment issue

[Tim Harvey]

I noticed what I believe is a bug in xmlparse.cpp but wanted to make
sure its really a bug before I posted a patch.

'center' alignment I believe should make the widget be centered
horizontally but not vertically as there are alignment types of
'vcenter' and 'allcenter' to handle vertical centering.  However I
noticed that whenever xmlparse.cpp catches 'center' it sets
justification to 'Qt::AlignCenter' which is both horiz + vert centering.
I believe it should set 'Qt::AlignHCenter'.

I tracked this down because of a specific label widget in the
VideoManager that was centered horizontally at the bottom of the screen,
yet its vertical placement was not in line with two other labels which
were to the right and left.  Making the above change fixed that, but I
worry that it could end up skewing vertical placements of other UIType's
that use 'center' alignment.  I've made the change on my local version
and don't see any negative effects yet.

Thoughts?

Tim