Fix illegal encoded high/low surrogate pairs.

gistfile1.txt

StringBuilder f = new StringBuilder(w.length());
for (int i = 0; i < w.length(); i++)
{
	char c = w.charAt(i);
	if (c >= 0xD800 && c <= 0xD8FF)
	{
		int h = ((c - 0xD800) * 0x400);
		int l = ((w.charAt(++i) - 0xDC00) + 0x10000);
		f.append((char) (h + l));
	}
	else
	{
		f.append(c);
	}
}
return f.toString();