fails:IO#sysread on a file reads the specified number of bytes from the file to the buffer
fails:IO#sysread on a file coerces the second argument to string and uses it as a buffer
fails:IO#sysread on a file throws IOError when called immediately after a buffered IO#read
fails:IO#sysread on a file does not raise error if called after IO#read followed by IO#syswrite
fails:IO#sysread on a file raises IOError on closed stream
