[FEATURE] Display in EM what PHP extension is available

Change-Id: I5c88eea95b6689d893a457f63783bb3db8f0ae86
Releases: 2.1
Resolves: #62199
Reviewed-on: http://review.typo3.org/33295
Reviewed-by: Fabien Udriot <fabien.udriot@ecodev.ch>
Tested-by: Fabien Udriot <fabien.udriot@ecodev.ch>