[FEATURE] Use wt_spamshield old mailform on TYPO3 >= 4.6
Resolves: #52840
Releases: 6.1, 6.0, 4.7, 4.5

Change-Id: I7d2a835c5733a74136463ec205fbd36047a894ff
Reviewed-on: https://review.typo3.org/25334
Reviewed-by: Ralf Zimmermann
Tested-by: Ralf Zimmermann