[TASK] Remove explicit checks for PHP < 5.3

Make PHP 5.3 a requirement for TYPO3 4.6 and remove tests that check for older
versions of PHP.

Change-Id: Ib73e332a44f618e59f78c8e442d2bf27474c4964
Resolves: #25395
Reviewed-on: http://review.typo3.org/1277
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog