Fixes to StreamExts.

- Almost all calls to Stream.Read were broken. These have been patched to all go through ReadBytes which itself has been fixed to function correctly. The key thing to note is that Stream.Read is very much allowed to return less than the requested number of bytes. If this happens and you're not checking the return result, you'll be working with partially initialized arrays and really bad stuff happens when you do that.
- Call CopyTo rather than copying between streams manually.
- Peek and ReadUInt8 have been changed to avoid a pointless array allocation which is significant overhead for such simple calls.

OpenRA.Game/StreamExts.cs

@@ -21,27 +21,38 @@ namespace OpenRA
 		{
 			if (count < 0)
 				throw new ArgumentOutOfRangeException("count", "Non-negative number required.");
+			var buffer = new byte[count];
+			s.ReadBytes(buffer, 0, count);
+			return buffer;
+		}
 
-			var buf = new byte[count];
-			if (s.Read(buf, 0, count) < count)
-				throw new EndOfStreamException();
-
-			return buf;
+		public static void ReadBytes(this Stream s, byte[] buffer, int offset, int count)
+		{
+			while (count > 0)
+			{
+				int bytesRead;
+				if ((bytesRead = s.Read(buffer, offset, count)) == 0)
+					throw new EndOfStreamException();
+				offset += bytesRead;
+				count -= bytesRead;
+			}
 		}
 
 		public static int Peek(this Stream s)
 		{
-			var buf = new byte[1];
-			if (s.Read(buf, 0, 1) == 0)
+			var b = s.ReadByte();
+			if (b == -1)
 				return -1;
-
-			s.Seek(s.Position - 1, SeekOrigin.Begin);
-			return buf[0];
+			s.Seek(-1, SeekOrigin.Current);
+			return (byte)b;
 		}
 
 		public static byte ReadUInt8(this Stream s)
 		{
-			return s.ReadBytes(1)[0];
+			var b = s.ReadByte();
+			if (b == -1)
+				throw new EndOfStreamException();
+			return (byte)b;
 		}
 
 		public static ushort ReadUInt16(this Stream s)
@@ -87,19 +98,9 @@ namespace OpenRA
 		public static string ReadASCIIZ(this Stream s)
 		{
 			var bytes = new List<byte>();
-			var buf = new byte[1];
-
-			for (;;)
-			{
-				if (s.Read(buf, 0, 1) < 1)
-					throw new EndOfStreamException();
-
-				if (buf[0] == 0)
-					break;
-
-				bytes.Add(buf[0]);
-			}
-
+			byte b;
+			while ((b = s.ReadUInt8()) != 0)
+				bytes.Add(b);
 			return new string(Encoding.ASCII.GetChars(bytes.ToArray()));
 		}
 
@@ -113,11 +114,7 @@ namespace OpenRA
 		public static byte[] ReadAllBytes(this Stream s)
 		{
 			using (s)
-			{
-				var data = new byte[s.Length - s.Position];
-				s.Read(data, 0, data.Length);
-				return data;
-			}
+				return s.ReadBytes((int)(s.Length - s.Position));
 		}
 
 		public static void Write(this Stream s, byte[] data)