Merge remote-tracking branch 'upstream/master'
Included missing periods
[node-view] Use 'hidden' as the attribute's value

Even though the attribute's effect gets activated for any value of the
attribute, this way it's easier for anyone looking at the DOM to figure
out what the visibility of the node is.
[node-view] Document node._isHidden
Merge branch 'node-hidden' into dev-master
Merge branch 'dev-master' into dev-3.x
Editor: IE 11 no longer supports `document.selection`, in favor of `window.getSelection`.
Editor: Build.
[event-custom] Document defaultTargetOnly flag
Merge branch 'live-docs' into dev-master
Merge branch 'dev-master' into dev-3.x
Remove `X-Requested-With` info in XDR example

This is no longer necessary as using `xdr: native` will remove
all custom headers for you by default.
fix typo in docs
Merge branch 'dd-typo' of github.com:smikes/yui3 into smikes-dd-typo
Merge branch 'live-docs' into dev-master
Merge branch 'dev-master' into dev-3.x
[docs] Replace variants of Number
[docs] Replace variants of undefined
[docs] Replace variants of HTMLElement
[docs] Replace variants of Function