[PECOFF] Add one more test for r203875.

This is to make sure that the Windows-style command line tokenizer is
working as expected.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@203877 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Implement /lib option.

This option is not documented and seems weird, but yeah we need it anyway.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@203884 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Make WinLinkDriver::parse() and allocate*() functions thread-safe.

Looks like a major cause of instability on Windows is this thread-safety bug.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@203889 91177308-0d34-0410-b5e6-96231b3b80d8