Visual Studio 2015/2017 cannot handle that correctly, and emits a lot
of intellisense errors. So, just prepend the define with "ShellClass_"

Change-Id: I473ceb7e0a88e114b92e6342fd4ae63015cafd3e
Reviewed-on: https://gerrit.libreoffice.org/51135Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>