Fix the haddock tests when going via C

We need to have a header which claims the foreign imports we do are
for entities that actually exist. Otherwise the C compiler complains.

testsuite/tests/ghc-regress/haddock/haddock_examples/Test.hs

@@ -253,7 +253,7 @@ We can also include URLs in documentation: <http://www.haskell.org/>.
 f :: C a => a -> Int
 
 -- | we can export foreign declarations too
-foreign import ccall g :: Int -> IO CInt
+foreign import ccall "header.h" g :: Int -> IO CInt
 
 -- | this doc string has a parse error in it: \'
 h :: Int
@@ -380,7 +380,7 @@ newn = undefined
 
 
 -- | A foreign import with argument docs
-foreign import ccall unsafe 
+foreign import ccall unsafe "header.h"
  o :: Float  -- ^ The input float
    -> IO Float  -- ^ The output float
 

testsuite/tests/ghc-regress/haddock/haddock_examples/haddock.Test.stderr

@@ -96,7 +96,7 @@ data R1
 <document comment>
 f :: (C a) => a -> Int
 <document comment>
-foreign import ccall safe "static  &g" g :: Int -> IO CInt
+foreign import ccall safe "static header.h &g" g :: Int -> IO CInt
 <document comment>
 h :: Int
 h = 42
@@ -131,7 +131,7 @@ m :: R -> N1 () <document comment> -> IO Int <document comment>
 newn :: R <document comment> -> N1 () <document comment> -> IO Int
 newn = undefined
 <document comment>
-foreign import ccall unsafe "static  &o" o :: Float <document comment>
+foreign import ccall unsafe "static header.h &o" o :: Float <document comment>
 					      -> IO Float <document comment>
 <document comment>
 newp :: Int

testsuite/tests/ghc-regress/haddock/haddock_examples/header.h

+
+/* These are used in Test.hs */
+extern int g(HsInt x);
+extern HsFloat o(HsFloat x);
+