#74 `l` should not return linefeeds

[Dennis]

Normally, l returns the contents of a line without the trailing linefeed.

However, calling l when there's nothing left to read returns the string "\n", even when STDIN is completely empty.

This makes looping over lines of input (e.g., l{...l}h) inconvenient, since it will print a linefeed too many and exit with an error.

[aditsu]

Well, what else could it return that would not be ambiguous?