Remove undocumented `global` object aliases.

[jdalton]

There are a couple of undocumented global object aliases root and GLOBAL that could be removed. I've stumbled on root in lodash that was interesting to debug.

[rlidwka]

nodejs/node-v0.x-archive#8156

+1

[silverwind]

I think GLOBAL was the initial global object name, so there might be some ancient code that relies on it. Would love to see some npm stats for usage on these two.

[ChALkeR]

Should be linked with this: #1794
Once #1794 gets merged, this will need alterations in the .eslintrc file.

Edit: Ah, this is not a PR, sorry. ☺

[silverwind]

@JacksonTian care to port nodejs/node-v0.x-archive#8156 to io.js?

[JacksonTian]

Ok.

[JacksonTian]

The new PR is here #1838.

[jasnell]

Closing this since #1838 landed.