Lucene.Net.Support.IO.FileSupport::fileCanonPathCache is not thread safe

Lucene.Net.Support.IO.FileSupport is a static class with a normal dictionary used as a cache. If called concurrently multiple times (enough to force the dictionary to resize), concurrent calls will fail with an IndexOutOfRangeException

private static readonly IDictionary<string, string> fileCanonPathCache = new Dictionary<string, string>();