Add tasks for all the new languages

Task/Executable-library/Sidef/executable-library-1.sidef

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+func hailstone(n) {
+    gather {
+        while (n > 1) {
+            take(n)
+            n = (n.is_even ? n/2 : (3*n + 1))
+        }
+        take(1)
+    }
+}
+ 
+if (__FILE__ == __MAIN__) {             # true when not imported
+    var seq = hailstone(27)
+    say "hailstone(27) - #{seq.len} elements: #{seq.ft(0, 3)} [...] #{seq.ft(-4)}"
+ 
+    var n = 0
+    var max = 0
+    100_000.times { |i|
+        var seq = hailstone(i)
+        if (seq.len > max) {
+            max = seq.len
+            n = i
+        }
+    }
+ 
+    say "Longest sequence is for #{n}: #{max}"
+}

Task/Executable-library/Sidef/executable-library-2.sidef

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+$ sidef Hailstone.sm

Task/Executable-library/Sidef/executable-library-3.sidef

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+include Hailstone
+ 
+var score = Hash()
+100_000.times { |i| score{ Hailstone::hailstone(i).len } := 0 ++ }
+ 
+var k = score.keys.max_by {|k| score{k} }
+say "Most common length is #{k}, occurring #{score{k}} times"

Task/Executable-library/Sidef/executable-library-4.sidef

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+$ sidef test_hailstone.sf