[BUGFIX] Escape regex chars when building sWordRegEx

The submitted sword_list GET parameters are parsed through
preg_quote() when loaded into  TSFE->sWordRegEx to prevent
invalid regular expressions.

The initialization is moved to a seperate method
PageGenerator::initializeSearchWordDataInTsfe() and unit
tests are added.

Releases: master, 6.2
Resolves: #41728
Change-Id: Id96fd5e201c25b06001f7e1c7811d6c38239aafa
Reviewed-on: http://review.typo3.org/37328


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>