TPageControl page area is outside of the form on Ubuntu 18/20

[Alex Egorov]

May be this bug is related to Issue #292, may be not.

How to reproduce:
1. Put Pages: TPageControl on the form; Pages.Align := Client
2. Add Page to the Pages
3. Add Panel to the Page; Panel.Align := Client; Panel.AlignWidhMargins := True; Panel.Margins = (0, 0, 0, 0)

• On the Indows we can see Panel completely
• On the Ubuntu 18 to make in visible completely Panel.Margins.Bottom should be = 7
• On the Ubuntu 20 it should be = 18