Fix documentation install on Windows

Currently the libisc.vcxproj contains stuff like this:

echo Copying the ARM and the Installation Notes.

copy ..\COPYRIGHT ..\Build\Release
copy ..\README ..\Build\Release
copy ..\HISTORY ..\Build\Release
copy readme1st.txt ..\Build\Release
copy index.html ..\Build\Release
copy ..\doc\arm\*.html ..\Build\Release
copy ..\doc\arm\Bv9ARM.pdf ..\Build\Release
copy ..\CHANGES ..\Build\Release
if Exist ..\CHANGES.SE copy ..\CHANGES.SE ..\Build\Release
copy ..\FAQ ..\Build\Release

As we currently don't build the documentation on Windows and we don't store it in git, I think the right way forward is to cherry-pick the artifact files from the docs build into the Windows zip file.