fix issue with printing scheme (FBD, LD or SFC) with comment element on GNU/Linux

If you draw FBD scheme and place comment on it and then try to print
it, then no wires will be printed and comment box is empty (text is
missing). This happens only for wx.PrinterDC and not on wx.MemoryDC
that is used to draw print preview window in Beremiz IDE.
Looks like a bug in wxPython or wxWidgets.

There were found several workaround for this issue.
1) If some dc.DrawLines call is placed before dc.DrawPolygon, then the
problem is gone.

...
dc.DrawLines(polygon)
dc.DrawPolygon(polygon)
...

2) Reseting DC brush solves the problem as well (see this changeset).

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