Rewrote free disk space checking code

Moving the portability handling into a small C library cleans up things
a lot, avoiding the pain of unpacking structs from inside haskell code.

Build/Configure.hs

@@ -10,12 +10,8 @@ import Control.Applicative
 import Build.TestConfig
 import Utility.SafeCommand
 
-tests :: Bool -> [TestCase]
-tests True = cabaltests ++ common
-tests False = common
-
-common :: [TestCase]
-common =
+tests :: [TestCase]
+tests =
 	[ TestCase "version" getVersion
 	, TestCase "git" $ requireCmd "git" "git --version >/dev/null"
 	, TestCase "git version" getGitVersion
@@ -32,11 +28,6 @@ common =
 	, TestCase "ssh connection caching" getSshConnectionCaching
 	] ++ shaTestCases [1, 256, 512, 224, 384]
 
-cabaltests :: [TestCase]
-cabaltests =
-	[ TestCase "StatFS" testStatFSDummy
-	]
-
 shaTestCases :: [Int] -> [TestCase]
 shaTestCases l = map make l
 	where make n =
@@ -81,10 +72,6 @@ getSshConnectionCaching :: Test
 getSshConnectionCaching = Config "sshconnectioncaching" . BoolConfig <$>
 	boolSystem "sh" [Param "-c", Param "ssh -o ControlPersist=yes -V >/dev/null 2>/dev/null"]
 
-testStatFSDummy :: Test
-testStatFSDummy = 
-	return $ Config "statfs_sanity_checked" $ MaybeBoolConfig Nothing
-
 {- Set up cabal file with version. -}
 cabalSetup :: IO ()
 cabalSetup = do