Propagate section from base to derived symbol.

We were already propagating the section in

a = b

With this patch we also propagate it for

a = b + 1

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204581 91177308-0d34-0410-b5e6-96231b3b80d8
Add back tests that were reverted in r204203.

They pass again with the fix in r204581.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204582 91177308-0d34-0410-b5e6-96231b3b80d8