[!!!][TASK] Remove $GLOBALS['CLIENT']

The global client information is not useful any more nowadays
and can be removed. It is only used a few times in the core.
These usages are also removed now.

GeneralUtility::clientInfo() is kept for now.

Releases: master
Resolves: #68150
Change-Id: If339ed729b6c441496548cdd15a36c7943c69ae6
Reviewed-on: http://review.typo3.org/41261


Reviewed-by: Benjamin Mack <benni@typo3.org>
Reviewed-by: David Greiner <hallo@davidgreiner.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>