Add noUnusedLocals tsconfig flag, fix issues

Two parts were commented out:
- _writeStopped: This is because _xoffSentToCatchUp references this variable
  and the feature is sort of half implemented/disabled.
- _clearChar: This is because some comments still reference this, it's part
  of the work needed to do better line redrawing.

src/SelectionManager.test.ts

@@ -6,11 +6,10 @@
 import jsdom = require('jsdom');
 import { assert } from 'chai';
 import { CharMeasure } from './utils/CharMeasure';
-import { CircularList } from './utils/CircularList';
 import { SelectionManager } from './SelectionManager';
 import { SelectionModel } from './SelectionModel';
 import { BufferSet } from './BufferSet';
-import { LineData, CharData, ITerminal, ICircularList, IBuffer } from './Types';
+import { LineData, CharData, ITerminal, IBuffer } from './Types';
 import { MockTerminal } from './utils/TestUtils.test';
 
 class TestMockTerminal extends MockTerminal {
@@ -39,11 +38,9 @@ class TestSelectionManager extends SelectionManager {
 describe('SelectionManager', () => {
   let dom: jsdom.JSDOM;
   let window: Window;
-  let document: Document;
 
   let terminal: ITerminal;
   let buffer: IBuffer;
-  let rowContainer: HTMLElement;
   let selectionManager: TestSelectionManager;
 
   beforeEach(() => {