Fix three broken tests involving exceptions

See comment:16 in Trac #10712. The tests were wrong, not GHC!

testsuite/tests/concurrent/should_run/T3279.hs

@@ -7,7 +7,7 @@ import GHC.IO (unsafeUnmask)
 
 f :: Int
 f = (1 +) . unsafePerformIO $ do
-        error "foo" `catch` \(SomeException e) -> do
+        throwIO (ErrorCall "foo") `catch` \(SomeException e) -> do
             myThreadId >>= flip throwTo e
             -- point X
             unsafeUnmask $ return 1
@@ -22,4 +22,4 @@ main = do
     yield
     -- should print 1 + 1 = 2
     print f
-    
+

testsuite/tests/concurrent/should_run/conc012.hs

@@ -14,8 +14,8 @@ stackoverflow n = n + stackoverflow n
 
 main = do
   let x = stackoverflow 1
-  result <- newEmptyMVar 
-  forkIO $ Control.Exception.catch (x `seq` putMVar result Finished) $
+  result <- newEmptyMVar
+  forkIO $ Control.Exception.catch (evaluate x >> putMVar result Finished) $
 		     \e -> putMVar result (Died e)
   res <- takeMVar result
   case res of

testsuite/tests/concurrent/should_run/conc014.hs

@@ -8,14 +8,12 @@ main = do
   main_thread <- myThreadId
   m <- newEmptyMVar
   forkIO (do { takeMVar m;  throwTo main_thread (ErrorCall "foo") })
-  (do 
-     error "wibble"
-	`Control.Exception.catch`
+  (do { throwIO (ErrorCall "wibble")
+	  `Control.Exception.catch`
 	    (\e -> let _ = e::ErrorCall in
-                   do putMVar m (); sum [1..10000] `seq` putStrLn "done.")
-     myDelay 500000
-   )
-    `Control.Exception.catch` 
+                   do putMVar m (); evaluate (sum [1..10000]); putStrLn "done.")
+       ; myDelay 500000 })
+    `Control.Exception.catch`
        \e -> putStrLn ("caught: " ++ show (e::SomeException))
 
 -- compensate for the fact that threadDelay is non-interruptible