Force LTR for the terminal element

Issue #1330: This prevents RTL layouts from mishandlin the
intended layout of the terminal container and children.

src/Terminal.ts

@@ -622,6 +622,7 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
 
     // Create main element container
     this.element = this._document.createElement('div');
+    this.element.dir = "ltr";   //xterm.css assumes LTR
     this.element.classList.add('terminal');
     this.element.classList.add('xterm');
     this.element.setAttribute('tabindex', '0');