For COFF only: dwarf debug info output a label reference as a section relative item only when it's one of dw_from strp, sec_offset, ref_addr or op_call_ref instead of going by size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188296 91177308-0d34-0410-b5e6-96231b3b80d8