Instead:

- create it early in Window::ImplInit(), except for the default window
  (that one is a chicken-and-egg problem, as creating a VirtualDevice
  invokes ImplGetDefaultWindow(), but creating the default window then
  would create a VirtualDevice)
- only erase the painted area of the buffer, don't create it
- use a separate bool in the frame state to track if we're in the middle
  of a (possibly recursive) buffered paint

And with that, rename CreateBuffer() to StartBufferedPaint(), as it does
not create the buffer anymore.

Change-Id: Ib33e8afa36977aa809f0ea2158a369f288cba8c7
(cherry picked from commit ea5e83ab)
Reviewed-on: https://gerrit.libreoffice.org/17445Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>