vcl/source: get rid of redundant svsys.h includes

+ adapted for WNT (it does really need it for app/settings.cxx)

Change-Id: I33a65d24f7c6c46a36718e4421ae88de180a9739
Reviewed-on: https://gerrit.libreoffice.org/11814
Reviewed-by: Douglas Mencken <dougmencken@gmail.com>
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>