testsuite: Increase width of stack003 test

Previously the returned tuple seemed to fit in registers on amd64. This
meant that non-moving collector bug would cause the test to fail on i386
yet not amd64.

testsuite/tests/rts/stack003.hs

@@ -6,12 +6,18 @@ import System.Environment
 main = do
   [n] <- fmap (fmap read) getArgs
   case g n of
-    (# a, b, c, d, e, f, g, h, i #) -> print a
+    (# a, b, c,  d, e, f,  g, h, i,  j, k, l #) -> print a
 
 -- a deep stack in which each frame is an unboxed tuple-return, to exercise
 -- the stack underflow machinery.
-g :: Int -> (# Int,Float,Double,Int#,Float#,Double#,Int,Float,Double #)
-g 0 = (# 1, 2.0, 3.0, 1#, 2.0#, 3.0##, 1, 2.0, 3.0 #)
+g :: Int -> (# Int,Float,Double,
+               Int#,Float#,Double#,
+               Int,Float,Double,
+               Int#,Float#,Double# #)
+g 0 = (# 1, 2.0, 3.0,
+         1#, 2.0#, 3.0##,
+         1, 2.0, 3.0,
+         1#, 2.0#, 3.0## #)
 g x = case g (x-1) of
-        (# a, b, c, d, e, f, g, h, i #) ->
-          (# a+1, b, c, d, e, f, g, h, i #)
+        (# a, b, c,  d, e, f,  g, h, i,  j, k, l #) ->
+          (# a+1, b, c,  d, e, f,  g, h, i,  j, k, l #)