This was lost in commit 1698debe.
Windows 10 SDK doesn't depend on it, but Windows 8.1 SDK does,
because InitPropVariantFromString is implemented in it as call
to SHStrDupW.

Change-Id: I20b596bba21664bed93d2b194f6cc9f23673586a
Reviewed-on: https://gerrit.libreoffice.org/61612
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>