Allow mousedown even to propagate on right click
Allow mousedown even to propagate on right click

Fixes #913

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