[System.IO.Compression] Fixed re-opening of disposed Zip entry streams.

Fixes System.IO.Compression to work against Microsoft Office OpenXML SDK which depends on this behavior.

Also partial fix for https://bugzilla.xamarin.com/show_bug.cgi?id=33553.

mcs/class/System.IO.Compression/Test/System.IO.Compression/ZipTest.cs

@@ -114,6 +114,51 @@ public void ZipGetEntryOpen()
 			File.Delete ("test.zip");
 		}
 
+		[Test]
+		public void ZipOpenAndReopenEntry()
+		{
+			try {
+				File.Copy("archive.zip", "test.zip", overwrite: true);
+				using (var archive = new ZipArchive(File.Open("test.zip", FileMode.Open),
+					ZipArchiveMode.Update))
+				{
+					var entry = archive.GetEntry("foo.txt");
+					Assert.IsNotNull(entry);
+
+					var stream = entry.Open();
+
+					try {
+						stream = entry.Open();
+					} catch (global::System.IO.IOException ex) {
+						return;
+					}
+
+					Assert.Fail();
+				}
+			} finally {
+				File.Delete ("test.zip");
+			}
+		}
+
+
+		[Test]
+		public void ZipOpenCloseAndReopenEntry()
+		{
+			File.Copy("archive.zip", "test.zip", overwrite: true);
+			using (var archive = new ZipArchive(File.Open("test.zip", FileMode.Open),
+				ZipArchiveMode.Update))
+			{
+				var entry = archive.GetEntry("foo.txt");
+				Assert.IsNotNull(entry);
+
+				var stream = entry.Open();
+				stream.Dispose();
+				stream = entry.Open();
+			}
+
+			File.Delete ("test.zip");
+		}
+
 		[Test]
 		public void ZipGetEntryDeleteReadMode()
 		{

mcs/class/System.IO.Compression/ZipArchiveEntry.cs

@@ -29,10 +29,96 @@
 
 namespace System.IO.Compression
 {
+	internal class ZipArchiveEntryStream : Stream, IDisposable
+	{
+		private readonly ZipArchiveEntry entry;
+		private readonly Stream stream;
+
+		public override bool CanRead {
+			get { 
+				return stream.CanRead;
+			}
+		}
+
+		public override bool CanSeek {
+			get {
+				return stream.CanSeek;
+			}
+		}
+
+		public override bool CanWrite {
+			get {
+				return stream.CanWrite;
+			}
+		}
+
+		public override long Length {
+			get {
+				return stream.Length;
+			}
+		}
+
+		public override long Position {
+			get {
+				return stream.Position;
+			}
+			set {
+				stream.Position = value;
+			}
+		}
+
+		public ZipArchiveEntryStream(ZipArchiveEntry entry, Stream stream)
+		{
+			this.entry = entry;
+			this.stream = stream;
+		}
+
+		public override void Flush ()
+		{
+			stream.Flush();
+		}
+
+		public override long Seek (long offset, SeekOrigin origin)
+		{
+			return stream.Seek(offset, origin);
+		}
+
+		public override void SetLength (long value)
+		{
+			stream.SetLength(value);
+		}
+
+		public override int Read (byte[] buffer, int offset, int count)
+		{
+			return stream.Read(buffer, offset, count);
+		}
+
+		public override void Write (byte[] buffer, int offset, int count)
+		{
+			stream.Write(buffer, offset, count);
+		}
+
+		public new void Dispose()
+		{
+			Dispose(true);
+			GC.SuppressFinalize(this);
+			base.Dispose();
+		}
+
+		protected override void Dispose(bool disposing)
+		{
+			if (disposing) 
+			{
+				entry.openStream = null;
+				stream.Dispose();
+			}
+		}
+	}
+
 	public class ZipArchiveEntry
 	{
 		readonly SharpCompress.Archive.Zip.ZipArchiveEntry entry;
-		private Stream openStream;
+		internal ZipArchiveEntryStream openStream;
 		private bool wasDeleted;
 
 		internal ZipArchiveEntry(ZipArchive	archive, SharpCompress.Archive.Zip.ZipArchiveEntry entry)
@@ -112,7 +198,7 @@ public Stream Open()
 			if (Archive.Mode == ZipArchiveMode.Create && openStream != null)
 				throw new IOException("The archive for this entry was opened with the Create mode, and this entry has already been written to.");
 
-			openStream = entry.OpenEntryStream();
+			openStream = new ZipArchiveEntryStream(this, entry.OpenEntryStream());
 
 			return openStream;
 		}