Issue #3079

So that the helper mechanism can meaningfully be used to register
asynchronous linters.

Use host property, not root.

Easiest to see the difference on touch-enabled device. Go to Tern demo
page (link below), click on a variable name and press Ctrl+I. Now pan
the editor's content. The tooltip stays at a fixed position, whilst
the variable name detaches and moves off.

The fix listens to scroll and blur, switching the tooltip off.

Issue #3055

Issue #3039

Opening the documentation in the same window navigates away from the
code editor.

So that the CodeMirror.Pass it will return actually ends up in the editor.

Closes #3040

See http://discuss.codemirror.net/t/simple-mode-and-anchored-regexp/88/4

Closes #3028

Issue #3017

See http://discuss.codemirror.net/t/jittering-mousewheel-scrolling-with-merge-addon-align-mode/125

See http://discuss.codemirror.net/t/possible-bug-in-simple-mode-indenting-behavior/109

Issue #2991

Closes #2983

The code was confused beyond belief, and the hintWords
functionality will provide the same completion power
without loading an additional addon.

Completing inside a word used to try and take the whole word into
account. This is not typical completion behavior, and often not what
you want. After this change, the addons only take the part of the
word in front of the cursor into account.

Allows convenient showing of panels (DOM nodes) above or
below an editor, automatically shrinking the editor to make
space.

Using the collapseIdentical option.

When closeOnEnter is disabled the enter event never gets default
prevented this causes issues for IE9/10, this way implementors can
optionally preventDefault if they want