[TASK] Use autoloader in rsaauth system extension

Resolves: #29142
Releases: 4.6

Change-Id: I5ee0161a49d22c9d29b82bebfce6a16d3f1a439d
Reviewed-on: http://review.typo3.org/4461
Reviewed-by: Georg Ringer
Reviewed-by: Xavier Perseguers
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog