Move SimpleAtoms.h to ReaderWriter.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@173380 91177308-0d34-0410-b5e6-96231b3b80d8
[Driver] Run the pass manager.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@173381 91177308-0d34-0410-b5e6-96231b3b80d8