Preserve class name added by renderLine event handler

Issue #2564
Add a bias option for selection operations

Issue #2560
[comment addon] Adjust docs for padding

Closes #2391
Closes #2387
Remove version numbers from script headers again

Bumping them for every release just adds too much git
noise and history blowup.
Mark release 4.2
Bump version number post-4.2
合并 CodeMirror 最新版本 4.2.1
update: 编译最新代码