Move access to SystemDependentDataHolder to SalBitmap

To be able to buffer BitmapData which is created based on
Bitmap class data, move the access to
basegfx::SystemDependentDataHolder from classes where it
was used until now (WinSalBitmap and SvpSalBitmap) up to
SalBitmap which is accessible outside vcl.

This is a reorder plus a virtual access method to
detect/access that helper layer, no functional change.
It will be needed for system-dependent renderers when
they want to use that standard buffering e.g. already
used in the headless & windows backends.

Change-Id: Ib30e7b98e722b977bb0c87ad253e3ffc1841e87e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/141456
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>

0 files changed, 0 insertions, 0 deletions