Change New Tai Lue shaping engine from SEA to default

This is to reflect the UTC decision to change the encoding model of
New Tai Lue from logical to visual to be similar to Thai, Lao, and
Tai Viet: http://www.unicode.org/L2/L2014/14250.htm#141-C26

The visual encoding is already the current practice of encoding New
Tai Lue on the web anyway:
http://www.unicode.org/L2/L2014/14195-newtailue.txt

Fixes behdad/harfbuzz#66.
1 file changed