Update target SDK to 25.
Update target SDK to 25.

- No known behavior changes, at least according to the docs at https://developer.android.com/reference/android/os/Build.VERSION_CODES.html#N_MR1
(cherry picked from commit c761cf9)

UweTrottmann/SeriesGuide,UweTrottmann/SeriesGuide,epiphany27/SeriesGuide