Reorganize tests and benchmark scripts.

Mainly to get rid of one top level directory. But this will
also be useful when there are tests of the embedding API.

test/benchmark/fannkuch.rb

@@ -0,0 +1,60 @@
+def fannkuch(n)
+  p = (0..n).to_a
+  s = p.dup
+  q = p.dup
+  sign = 1
+  sum = maxflips = 0
+  while(true)
+    # flip.
+
+    if (q1 = p[1]) != 1
+      q[0..-1] = p
+      flips = 1
+      until (qq = q[q1]) == 1
+        q[q1] = q1
+        if q1 >= 4
+          i, j = 2, q1 - 1
+          while i < j
+            q[i], q[j] = q[j], q[i]
+            i += 1
+            j -= 1
+          end
+        end
+        q1 = qq
+        flips += 1
+      end
+      sum += sign * flips
+      maxflips = flips if flips > maxflips # New maximum?
+
+    end
+    # Permute.
+
+    if sign == 1
+      # Rotate 1<-2.
+
+      p[1], p[2] = p[2], p[1]
+      sign = -1
+    else
+      # Rotate 1<-2 and 1<-2<-3.
+
+      p[2], p[3] = p[3], p[2]
+      sign = 1
+      i = 3
+      while i <= n && s[i] == 1
+        return [sum, maxflips] if i == n     # Out of permutations.
+
+        s[i] = i
+        # Rotate 1<-...<-i+1.
+
+        t = p.delete_at(1)
+        i += 1
+        p.insert(i, t)
+      end
+      s[i] -= 1  if i <= n
+    end
+  end
+end
+
+n = 9
+sum, flips = fannkuch(n)
+printf "%d\nPfannkuchen(%d) = %d\n", sum, n, flips