Restore using shlwapi by VCL code on Windows

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>

vcl/Library_vclplug_win.mk

@@ -87,6 +87,7 @@ $(eval $(call gb_Library_use_system_win32_libs,vclplug_win,\
     imm32 \
     ole32 \
     shell32 \
+    shlwapi \
     version \
     winspool \
 ))