Truncated strings mangle non-BMP Unicode characters

[franrogers]

If a string result exceeds what can fit in a single line of chat, truncating the end, non-BMP Unicode characters (i.e., surrogate pairs) get mangled. Por ejemplo:

[21:39:23]  <franny>     >> (function () { var s = ''; for (var i = 0; i < 108; i++) s = s + '\uD83D\uDCA9'; return s })();
[21:39:23]  <ecmabot-wm>     (string) '💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩💩'
[21:39:25]  <franny>     >> (function () { var s = ''; for (var i = 0; i < 109; i++) s = s + '\uD83D\uDCA9'; return s })();
[21:39:26]  <ecmabot-wm>     (string) 'ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð��©ð