Xpra: Ticket #1526: per-monitor DPI handling with MS Windows clients

Blocked by #56, X11 doesn't have per-monitor DPI data either.. so not very useful in the short term.

But we can get per-monitor DPI information:

$ from comtypes.client import CreateObject
s=o.ConnectServer('.', 'root\\cimv2')
res=s.ExecQuery('SELECT * FROM Win32_DesktopMonitor')
print([(x.Properties_['DeviceID'].Value, x.Properties_['PixelsPerXLogicalInch'].Value, x.Properties_['PixelsPerYLogicalInch'].Value,) for x in res])
[(u'DesktopMonitor1', 96, 96)]

Sat, 23 Jan 2021 05:26:44 GMT - migration script:

this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1526