Fix search for wide unicode
Fix search for wide unicode

Part of #1103

Tyriar/xterm.js,akalipetis/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js,akalipetis/xterm.js,sourcelair/xterm.js,Tyriar/xterm.js,akalipetis/xterm.js,akalipetis/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,sourcelair/xterm.js,Tyriar/xterm.js