Update charatlas when monitor DPI changes
Update charatlas when monitor DPI changes

Fixes #1118

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