MS ABI: Aligned tentative definitions don't have CommonLinkage

int __declspec(align(16)) foo; is a tentative definition but the storage
for that variable should not have CommonLinkage.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214828 91177308-0d34-0410-b5e6-96231b3b80d8
CodeGenObjCXX: Add a test for r214699

I forgot to add this with the changes for r214699.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214829 91177308-0d34-0410-b5e6-96231b3b80d8
ReleaseNotes: add blurb about Windows support

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214830 91177308-0d34-0410-b5e6-96231b3b80d8