Moving corlib files out of "System" directory into root

BeefLibs/corlib/src/IO/Substream.bf

@@ -0,0 +1,78 @@
+using System.IO;
+
+namespace System.IO
+{
+	class Substream : Stream
+	{
+		public bool mOwnsStream;
+		Stream mChildStream ~ { if (mOwnsStream) delete _; };
+		int64 mOffset;
+		int64 mLength;
+
+		public override int64 Position
+		{
+			get
+			{
+				return mChildStream.Position + mOffset;
+			}
+
+			set
+			{
+				mChildStream.Position = value + mOffset;
+			}
+		}
+
+		public override int64 Length
+		{
+			get
+			{
+				return mLength;
+			}
+		}
+
+		public override bool CanRead
+		{
+			get
+			{
+				return mChildStream.CanRead;
+			}
+		}
+
+		public override bool CanWrite
+		{
+			get
+			{
+				return mChildStream.CanWrite;
+			}
+		}
+
+
+		public this(Stream childStream, int64 offset, int64 length, bool ownsStream = false)
+		{
+			mChildStream = childStream;
+			mOffset = offset;
+			mLength = length;
+			mOwnsStream = ownsStream;
+		}
+
+		public override Result<int> TryRead(Span<uint8> data)
+		{
+			return mChildStream.TryRead(data);
+		}
+
+		public override Result<int> TryWrite(Span<uint8> data)
+		{
+			return mChildStream.TryWrite(data);
+		}
+
+		public override void Close()
+		{
+			mChildStream.Close();
+		}
+
+		public override void Flush()
+		{
+			mChildStream.Flush();
+		}
+	}
+}