add newtypes for QuickCheck to avoid LANG=C issues

All properties changed to use them, except for
prop_encode_c_decode_c_roundtrip, which already filtered to ascii
for other reasons.

A few modules had to be split out, because Setup does not build-depend
on QuickCheck.

Key.hs

@@ -31,7 +31,6 @@ module Key (
 	prop_isomorphic_key_encode
 ) where
 
-import Data.Char
 import qualified Data.Text as T
 import qualified Data.ByteString as S
 import qualified Data.Attoparsec.ByteString as A
@@ -100,16 +99,10 @@ instance Arbitrary KeyData where
 		<*> ((abs <$>) <$> arbitrary) -- chunksize cannot be negative
 		<*> ((succ . abs <$>) <$> arbitrary) -- chunknum cannot be 0 or negative
 
--- AssociatedFile cannot be empty, and cannot contain a NUL
--- (but can be Nothing). 
 instance Arbitrary AssociatedFile where
-  	arbitrary = (AssociatedFile . fmap conv <$> arbitrary)
-		`suchThat` (/= AssociatedFile (Just S.empty))
-		`suchThat` (\(AssociatedFile f) -> maybe True (S.notElem 0) f)
-	  where
-		-- Generating arbitrary unicode leads to encoding errors
-		-- when LANG=C, so limit to ascii.
-		conv = toRawFilePath . filter isAscii
+  	arbitrary = AssociatedFile
+		. fmap (toRawFilePath . fromTestableFilePath)
+		<$> arbitrary
 
 instance Arbitrary Key where
 	arbitrary = mkKey . const <$> arbitrary