fdo#67808 Fix Outline Font Effect support with CoreText

We add a new DrawTextSpecial() virtual to SalLayout
that allows to attempt to delegate font effects
to the underlying native graphic system.
The function return false if it was not capable of handling the effect,
true otherwise.
Right now only Outline Font effect on Coretext is actually handled that way.

OutPutDevice is augmented to attempt to delegate the font decoration
work, if the task was not handled properly it fallback on the generic code.

Note: ideally these effects should really be part of the FontSelector
info that is given during layoutting, and the layout should
indicate which of these decorations it was able to manage natively

but that is a much bigger architectural change.. this will do for now.

Change-Id: I5eb1a15e985cc3f234ec3dee899f349f309b42cb
Reviewed-on: https://gerrit.libreoffice.org/8599
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>