[PECOFF] Fix atom default alignment.
[PECOFF] Fix atom default alignment.

Alignment(1) does not mean that the atom should be aligned on a 1 byte
boundary but on a 2^1 boundary. So, atoms without any specific alignment
requirements should have Alignment(0).

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@190723 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld