On Linux, repaints are only issued if the number of received SHM
completion events matches the number of events initiated with
`xShmPutImage`.

Previously, destroying a GL context was calling `XSync (display, True)`
which cleared the event queue. Sometimes, this would cause an 'SHM
Completion Event' to be removed from the queue. This meant that the
number of received events would never match the number of initiated
events, and repainting would stop indefinitely.

By calling `XSync (display, False)` instead, we ensure that pending
events are kept in the queue, so any pending SHM completion event will
be found as usual during the next repaint timer callback.

Live calls getSize() before the plug-in has been attached to the system window and can query the correct system scale factor, this size is then used to resize the plug-in after it has been attached resulting in an unscaled window size.

On Windows, calls to `createSystemTypefaceFor` with a data buffer always
create a WindowsTypeface instance. However, calls with an existing
`Font` instance may try to create a WindowsDirectWriteTypeface, and will
only fall back to using a WindowsTypeface on failure.

Previously, a missing typeface wasn't treated as a failure, which meant
that `WindowsDirectWriteTypeface` would fall back to the first usable
typeface it could find.

With this change applied, we check whether the
WindowsDirectWriteTypeface actually managed to find the font we
requested, and will fall back to using a plain WindowsTypeface in that
case.