Backwards compatibility for io_read/io_write without offset.

Author: ioquatix

lib/async/scheduler.rb

@@ -161,11 +161,11 @@ def io_wait(io, events, timeout = nil)
 		end
 
 		if IO::Event::Support.buffer?
-			def io_read(io, buffer, length, offset)
+			def io_read(io, buffer, length, offset = 0)
 				@selector.io_read(Fiber.current, io, buffer, length, offset)
 			end
 
-			def io_write(io, buffer, length, offset)
+			def io_write(io, buffer, length, offset = 0)
 				@selector.io_write(Fiber.current, io, buffer, length, offset)
 			end
 		end