[TASK] Use (int) instead of intval() or (integer)

This patch replaces most of around 1600 occurrences of
intval() and every (integer) in the whole core.
Additionally it changes GeneralUtility::intExplode to use references
and typecasting as well.
Some occurrences of strstr() together with intval() have been replaced
with strpos() as well.
And some superfluous intval calls have been removed or reduced
to a single one i.e. for protected variables or before loops.
Patch updated after Core CGL decision from 30.01.2014

Resolves: #54265
Releases: 6.2
Change-Id: Iba57ffad1f4233ffa1a9f7d3ca5bfe9d2b53f1e8
Reviewed-on: https://review.typo3.org/26740
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind