Add a test for the difference between the H98 and the alternative layout rules

testsuite/tests/ghc-regress/layout/Makefile

+TOP=../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+layout001: %:
+	$(RM) $*.hi $*.o
+	echo Running with -XNoAlternativeLayoutRule
+	-"$(TEST_HC)" -XNoAlternativeLayoutRule -c $*.hs 2>&1
+	$(RM) $*.hi $*.o
+	echo Running with -XAlternativeLayoutRule
+	-"$(TEST_HC)" -XAlternativeLayoutRule -c $*.hs 2>&1
+

testsuite/tests/ghc-regress/layout/all.T

+
+test('layout001',
+     [extra_clean(['layout001.hi', 'layout001.o']),
+      only_compiler_types(['ghc'])],
+     run_command,
+     ['$MAKE -s --no-print-directory layout001'])
+

testsuite/tests/ghc-regress/layout/layout001.hs

+
+module M where
+
+f = case () of
+  () -> ()
+  where x = x

testsuite/tests/ghc-regress/layout/layout001.stdout

+Running with -XNoAlternativeLayoutRule
+Running with -XAlternativeLayoutRule
+
+layout001.hs:6:3: parse error on input `where'