Fix clipping of non-powerline chars
Fix clipping of non-powerline chars

See microsoft/vscode#152478

Tyriar/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js