[TASK] Remove class.tslib_pagegen.php from EXT:cms/tslib

Class is unused and contains code that is deprecated and
marked for removal in TYPO3 CMS 6.3

Resolves: #61231
Releases: 6.3
Change-Id: Ia0ec7aa95d54b0372edc340a8986a1d15c43d3e5
Reviewed-on: http://review.typo3.org/32458
Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>