Refactored some of the PollFD calls in AnonymousPipe class (PipeUnix.cs) to be slightly cleaner
Changed implementation of IsBroken() so that a Reader Stream (PipeDirection.In) that has pending data to be read, is not considered broken (that is, if there is data to be read, we don't started throwing exceptions about the writer end of the pipe being disconnected)
Changed the implementation WaitForPipeDrain() in AnonymousPipe so that if a writer calls/enters waits for pipe drain, then a context switch happens, then the client completse reading from the pipe and terminates (closing the pipe completely), when context switches back to the writer, the function returns cleanly instead of throwing a "Pipe is broken" exception. This is compatible with the microsoft implementation of theis method.
Accepted some slight reordering of outputs in unit test T108