wxMac 2.8.0: problem with wxALIGN_CENTER_VERTICAL

[Andrew Trevorrow]

After switching to wxMac 2.8.0 I've noticed an alignment problem when
wxALIGN_CENTER_VERTICAL is used to try and align the text baselines
in a wxStaticText box and a wxChoice box:

  http://www.trevorrow.com/wx/align-bug.png

The static text is 2 pixels too low.  The bug is also visible in the
dialogs sample -- see Aesthetics in the standard property sheet.

Andrew