add test for a bug in 6.8.2's handling of orphan modules

testsuite/tests/ghc-regress/driver/recomp005/A.hs

+module A where
+
+f :: Int -> Int
+f x = x + 1

testsuite/tests/ghc-regress/driver/recomp005/B.hs

+module B where
+
+g :: Int -> Int
+g x = x * 2
+

testsuite/tests/ghc-regress/driver/recomp005/C1.hs

+{-# -XRankNTypes #-}
+module C (f, g) where
+
+import A
+import B

testsuite/tests/ghc-regress/driver/recomp005/C2.hs

+{-# LANGUAGE RankNTypes #-}
+module C (f, g) where
+
+import A
+import B
+
+{-# RULES "f/g"  forall x . f (g x) = x #-}

testsuite/tests/ghc-regress/driver/recomp005/D.hs

+module D () where
+
+import C () -- so we don't get a dependency on C's export list

testsuite/tests/ghc-regress/driver/recomp005/E.hs

+module E where
+
+import D  -- get the RULE from C via D
+import A
+import B
+
+z = f (g 3)

testsuite/tests/ghc-regress/driver/recomp005/Makefile

+TOP=../../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+clean:
+	@rm -f *.o*
+	@rm -f *.hi*
+	@rm -f C.hs
+
+recomp005: clean
+	cp C1.hs C.hs
+	$(TEST_HC) --make E.hs -O
+	@sleep 1
+	cp C2.hs C.hs
+	# Should recompile E, because C is now an orphan
+	$(TEST_HC) --make E.hs -O

testsuite/tests/ghc-regress/driver/recomp005/all.T

+test('recomp005', skip_if_fast, run_command, ['$MAKE -s --no-print-directory recomp005'])
+
+if default_testopts.cleanup != '':
+    runCmd('$MAKE -C ' + in_testdir('') + ' clean')

testsuite/tests/ghc-regress/driver/recomp005/recomp005.stderr

+[1 of 5] Compiling B                ( B.hs, B.o )
+[2 of 5] Compiling A                ( A.hs, A.o )
+[3 of 5] Compiling C                ( C.hs, C.o )
+[4 of 5] Compiling D                ( D.hs, D.o )
+[5 of 5] Compiling E                ( E.hs, E.o )
+[3 of 5] Compiling C                ( C.hs, C.o )
+[4 of 5] Compiling D                ( D.hs, D.o )
+[5 of 5] Compiling E                ( E.hs, E.o )