[PECOFF] Optimize the writer a bit by removing a loop.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@196896 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Make more member functions non-virtual.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@196897 91177308-0d34-0410-b5e6-96231b3b80d8
Add explicit keyword.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@196898 91177308-0d34-0410-b5e6-96231b3b80d8