Bug 1085514 - Add Lollipop (v21) constants to Versions. r=me a=snorp

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extra : amend_source : c526a09a210f5fbe4f6925cb34fd7666182577a5
Bug 1098096 - Add a hack to make overscroll effect work on Android 5.0. r=lucasr, a=lsblakk