[PECOFF] Set section name for BSS atoms.

This change has no effect now, but will be needed to emit BSS atoms
to .bss section.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@193556 91177308-0d34-0410-b5e6-96231b3b80d8
Fix comment.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@193557 91177308-0d34-0410-b5e6-96231b3b80d8