Closes #1232

Splitting them into two spans apparently prevents them from rendering
at all (not unexpectedly).

The mechanism that was supposed to batch handlers during an operation and
fire them afterwards was broken -- handlers triggered during endOperation were
fired immediately.

Should be better now.

Closes #1226

It was still being called for showIfHidden widgets, even though it no longer exists.

Closes #1225

It was really quite misguided before.

Closes #1180

 - When mark-selection is deactivated the mark was not removed.
 - When mark-selection is [re]activated it immediately calls
   updateSelectedText() to set the mark if there's already a selection.
 - In addition to removing the mark, the handle is completely deleted
   to leave the CodeMirror instance in a clean state, and avoid re-deleting
   the mark if it's activated again.

This helps performance on v8 (in microbenchmarks) and is less noisy.

Regular literals are still accepted, the constructor is only used to create
objects, doesn't attach any methods.

Issue #1214

Issue #1206

Issue #1209

Issue #1076