Update examples

testsuite/reload/null/Makefile

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+TEST=   reload/null
+EXTRA_OBJS=Null.o
+TOP=../../..
+include ../../build.mk

testsuite/reload/null/Null.hs

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+module Null ( resource, resource_dyn )  where
+
+import API
+import Data.Dynamic
+import Prelude hiding (null)
+
+resource = null
+
+-- ! this has to be special: it can't be overridden by the user.
+resource_dyn :: Dynamic
+resource_dyn = toDyn resource

testsuite/reload/null/api/API.hs

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+{-# OPTIONS -fglasgow-exts #-}
+
+module API where
+
+import Data.Dynamic
+
+data Null = Null { a, b :: Int }
+   deriving (Typeable, Show)
+
+null :: Null
+null = Null { a = 42 , b = 1 }
+

testsuite/reload/null/prog/Main.hs

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+
+import System.Plugins
+import API
+
+-- an example where we just want to load an object and run it
+
+main = do 
+    m_v <- load "../Null.o" ["../api"] [] "resource"
+    (m,v) <- case m_v of
+        LoadSuccess m v -> return (m,v)
+        _               -> error "load failed"
+    putStrLn ( show (a v) )
+
+    m_v <- reload m "resource"   -- get a new version
+    v' <- case m_v of
+        LoadSuccess _ v -> return v
+        _               -> error "load failed"
+    putStrLn ( show (a v') )
+

testsuite/reload/null/prog/expected

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+42
+42