COFF: Better noexcept specification with LLVM_NOEXCEPT
COFF: Better noexcept specification with LLVM_NOEXCEPT

This is a follow-on to r238732


git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@238733 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld