[TASK] Add .gitattributes file

To convert file endings automatically to LF.

Change-Id: I3fb180b06366bb8ecbcc19146c606bbf5d998c65
Reviewed-on: http://review.typo3.org/32573
Reviewed-by: Armin Ruediger Vieweg <armin@v.ieweg.de>
Tested-by: Armin Ruediger Vieweg <armin@v.ieweg.de>