[PECOFF] Add /allowisolation command line option.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@191227 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Add comments to unit tests and reorder them if necessary.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@191228 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Add more tests for /machine, /base, /stack, /heap and /align.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@191229 91177308-0d34-0410-b5e6-96231b3b80d8