Handle dllexport for global aliases

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199205 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Handle dllexport for global aliases"

This reverts commit r199205.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199206 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Decouple dllexport/dllimport from linkage"

Revert this for now until I fix an issue in Clang with it.

This reverts commit r199204.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199207 91177308-0d34-0410-b5e6-96231b3b80d8