[runmode-stanadlone addon] Update with changes from runmode.js
[runmode-stanadlone addon] Update with changes from runmode.js

This PR updates the `runMode` function in runmode-standalone.js with 3 commits from [runmode.js](https://github.com/codemirror/CodeMirror/blob/master/addon/runmode/runmode.js):
- https://github.com/codemirror/CodeMirror/commit/7e35f03ad1639d92735c8dee1e1b5c86a727c873
- https://github.com/codemirror/CodeMirror/commit/53bc4b1f54670c827662d5210a37b35e63a07c39
- https://github.com/codemirror/CodeMirror/commit/64113ec97bb73c2a740d42d56021acb01ce05a92

The first commit from runmode.js allows the `callback` in runMode to be a function, as mentioned in https://codemirror.net/demo/runmode.html and https://discuss.codemirror.net/t/runmode-standalone-callback/2357. The last two commits fixes a copy-and-paste bug from IE.
codio/CodeMirror,wingify/CodeMirror,nightwing/CodeMirror,hackmdio/CodeMirror,wingify/CodeMirror,codio/CodeMirror,codio/CodeMirror,pabloferz/CodeMirror,dperetti/CodeMirror,nightwing/CodeMirror,pabloferz/CodeMirror,wingify/CodeMirror,hackmdio/CodeMirror,dperetti/CodeMirror,hackmdio/CodeMirror,dperetti/CodeMirror,nightwing/CodeMirror,pabloferz/CodeMirror