Enable lldb-server on Windows

Summary:
This commit contains three small changes to enable lldb-server on Windows.

- Add lldb-server for Windows to the build
- Disable pty redirection on Windows for the initial lldb-server bring up
- Add a support to get the parent pid for a process on Windows
- Ifdef some signals which aren't supported on Windows

Thanks to Hui Huang for the help with this patch!

Reviewers: labath

Reviewed By: labath

Subscribers: JDevlieghere, compnerd, Hui, amccarth, xiaobai, srhines, mgorny, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D61686

llvm-svn: 368774