Select the whole wrapped line when triple clicking

Fixes #1456

src/SelectionManager.ts

@@ -803,7 +803,9 @@ export class SelectionManager extends EventEmitter implements ISelectionManager
    * @param line The line index.
    */
   protected _selectLineAt(line: number): void {
-    this._model.selectionStart = [0, line];
-    this._model.selectionStartLength = this._terminal.cols;
+    const wrappedRange = this._buffer.getWrappedRangeForLine(line);
+    this._model.selectionStart = [0, wrappedRange.first];
+    this._model.selectionEnd = [this._terminal.cols, wrappedRange.last];
+    this._model.selectionStartLength = 0;
   }
 }