.NET 4.0 added the method Stream.CopyTo(stream, bufferSize). For .NET 3.5
and before, WebUtil defined an extension method for Stream with the signature
Stream.CopyTo(stream, maxBytesToCopy). The meaning of the second parameter
is different in the two forms and depending on which compiler and/or
runtime you use, you could get one form or the other. Crashes ensue.
This change renames the WebUtil stream copy method to something that
cannot be confused with the new CopyTo method defined in .NET 4.0.