tools: fix warnings in simplebench

tools/simplebench.hs

@@ -36,14 +36,10 @@ Summary (best iteration):
 
 -}
 
-import Data.Char
 import Data.List
-import Data.Maybe
-import Numeric
 import System.Environment
-import System.Directory
 import System.FilePath
-import System.Cmd
+import System.Process
 import System.IO
 import Text.Tabular
 import qualified Text.Tabular.AsciiArt as TA
@@ -52,10 +48,8 @@ import Text.Html ((+++), renderHtml, stringToHtml)
 import System.Exit
 import Text.Printf
 import Data.Time.Clock
-import Data.Time.Format
-import System.Locale
+import Data.Time.Format ()
 import Control.Monad
-import Debug.Trace
 import System.Console.GetOpt
 
 usagehdr = "bench [-f testsfile] [-n iterations] [-p precision] executable1 [executable2 ...]\n" ++
@@ -177,5 +171,3 @@ maketable opts rownames colnames results = Table rowhdrs colhdrs rows
 
 showtime :: [Opt] -> (Float -> String)
 showtime opts = printf $ "%." ++ show (precisionopt opts) ++ "f"
-
-strace a = trace (show a) a