...where the most plausible explanation for the bug's crash from within
ScGridWindow::CreateAccessible appears to be that the call to

  xAcc = new ScAccessibleEditObject(this, ...)

which stores "this" as a css::uno::Reference in the ScAccessibleEditObject, can
cause xAcc to be deleted synchronously from within the ScAccessibleDocument
ctor, causing the ScAccessibleDocument instance itself to also be deleted.

So re-use the existing ScAccessibleDocument::Init (already properly called at
the only place that instantiates ScAccessibleDocument, in
ScGridWindow::CreateAccessible) to defer any initialization that uses "this",
and hope that the resulting slight re-ordering of when certain initialization
code is executed does not cause problems.

Change-Id: I524a1659394e8900b7d33de358fdd4baf647c083
Reviewed-on: https://gerrit.libreoffice.org/18750Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>