v6 comboboxes default to displaying up to 30entries and
give a bad user experience in LiveCD
where we usually have low vertical screen resolution.
Therefore limit the height of the expanded boxes to
bring us close to how they were drawn before 0.4.12-dev-882-g
e3e173ffaa
Adding CBS_NOINTEGRALHEIGHT gives similar result for both:
comctl32 v5 and v6 comboboxes.
Similar commit for bootcd CORE-16252
went into 0.4.13-dev-740-g
8b67edd8fa
