Add tasks for all the new languages

Task/Binary-search/Futhark/binary-search.futhark

@@ -0,0 +1,13 @@
+fun main(as: [n]int, value: int): int =
+  let low = 0
+  let high = n-1
+  loop ((low,high)) = while low <= high do
+    -- invariants: value > as[i] for all i < low
+    --             value < as[i] for all i > high
+    let mid = (low+high) / 2
+    in if as[mid] > value
+       then (low, mid - 1)
+       else if as[mid] < value
+       then (mid + 1, high)
+       else (mid, mid-1) -- Force termination.
+  in low