(r55382) Removed U+200B, zero-width space, from the list of characters to be converte...

(r55382) Removed U+200B, zero-width space, from the list of characters to be converted to an underscore. This character is used in Khmer, Burmese and Thai (km, my, th) as an invisible word break indicator for the purposes of line wrapping. This is especially necessary for Khmer and Burmese since browsers do not have automatic word segmentation for those languages, like they do for Thai. It's not appropriate for these word break hints to be displayed as spaces.