Revert commit r219835 and r219829.

Revert "Correctly handle references to section symbols."
Revert "Allow forward references to section symbols."

Rui found a regression I am debugging.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220010 91177308-0d34-0410-b5e6-96231b3b80d8