Android UCI engine update: Corchess 1.8.20170831.ACH

This build comes from Alexei, as usual, given that he is the only build maker for Android remaining active except for a few engine authors, after Aart Bik, Jim Ablett and Aprijal Pasaribu stopped.

GET Corchess 1.8.20170831 for arm7 and arm8.

In case of trouble downloading from your PC, use your mobile device or refer to THIS POST.