Move a private field to private section.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@196562 91177308-0d34-0410-b5e6-96231b3b80d8
Move definitions to cpp file. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@196563 91177308-0d34-0410-b5e6-96231b3b80d8
Make error code variables to have narrower scope.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@196564 91177308-0d34-0410-b5e6-96231b3b80d8