Properly mark initial viewport lines as wrapped
Properly mark initial viewport lines as wrapped

Fixes #767

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