Added Queens benchmark from nofib

It currently fails with a segfault, probably due to lack of
heap overflow checks.

tests/Nofib/Queens.hs

@@ -0,0 +1,30 @@
+{-# LANGUAGE NoImplicitPrelude, MagicHash #-}
+-- RUN: %bc_vm_chk
+-- CHECK: @Result@ IND -> GHC.Bool.True`con_info
+-- XFAIL: *
+module Nofib.Queens where
+-- !!! count the number of solutions to the "n queens" problem.
+-- (grabbed from LML dist)
+
+import GHC.Types
+import GHC.Bool
+import GHC.Base
+import GHC.Num
+import GHC.List
+
+test = nsoln 10 == 724
+
+enumFromTo'Int :: Int -> Int -> [Int]
+enumFromTo'Int from@(I# m) to@(I# n) =
+  if m ># n then [] else
+    from : enumFromTo'Int (I# (m +# 1#)) to
+
+nsoln nq = length (gen nq)
+ where
+    safe :: Int -> Int -> [Int] -> Bool
+    safe x d []    = True
+    safe x d (q:l) = x /= q && x /= q+d && x /= q-d && safe x (d+1) l
+
+    gen :: Int -> [[Int]]
+    gen 0 = [[]]
+    gen n = [ (q:b) | b <- gen (n-1), q <- enumFromTo'Int 1 nq, safe q 1 b]