...macOS 10.9 reportedly doesn't yet support the 'CGContext' replacement, see
the comments to <https://gerrit.libreoffice.org/#/c/61353/>
"loplugin:redundantcast".

This reverts c3c88d6b "loplugin:redundantcast"
(whose commit message was rather misleading; the redundantcast warnings were
merely a follow-up to the commit's actual meat, of replacing deprecated uses of
'graphicsPort' with 'CGContext'; I had failed to realize that when I chunked the
various changes necessary for 10.14 into several individual commits) and adds
SAL_WNODEPRECATED_DECLARATIONS_PUSH/POP instead.

Change-Id: I778d7c3a29c780beff561fbbcc38df9e1494114c
Reviewed-on: https://gerrit.libreoffice.org/62815
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>