- 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

Issue #1203

Closes #1204

Issue #1203

Closes #1207

Issue #1198

Re-focusing is harmless on desktop browsers, and helps paper over
some browser bugs (such as firefox not 'really' focusing a textarea
in an iframe when the textarea is focused before the frame gains focus)

It had accidentally started taking window coordinates in the 3.0 refactor.

There's no guarantee that we'll be able to get the document from the parent
link (might not be set).

Closes #1199

Issue #1187

Issue #1194