lock listeners

[YoshihiroIto]

There is a problem with listeners becoming an exception during iteration.
This has been fixed in this pull request.

System.InvalidOperationException: InvalidOperation_EnumFailedVersion
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at TextMateSharp.Model.TMModel.Emit(ModelTokensChangedEvent e) in /_/src/TextMateSharp/Model/TMModel.cs:line 378
   at TextMateSharp.Model.TMModel.BuildEventWithCallback(Action`1 callback) in /_/src/TextMateSharp/Model/TMModel.cs:line 372
   at TextMateSharp.Model.TMModel.TokenizerThread.RevalidateTokens(Int32 startLine, Nullable`1 toLineIndexOrNull) in /_/src/TextMateSharp/Model/TMModel.cs:line 120
   at TextMateSharp.Model.TMModel.TokenizerThread.ThreadWorker(Object state) in /_/src/TextMateSharp/Model/TMModel.cs:line 101

[danipen]

Thanks for the contribution.

[danipen]

https://www.nuget.org/packages/TextMateSharp/1.0.65