add test from #799

testsuite/tests/ghc-regress/par/Makefile

+TOP=../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk

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

+setTestOpts(only_ways(['threaded1', 'threaded2']));
+
+test('par001', normal, compile_and_run, [''])

testsuite/tests/ghc-regress/par/par001.hs

+import Control.Parallel
+
+parfib 0 = return 1
+parfib 1 = return 1
+parfib n = do
+              n1 <- parfib (n - 1)
+              n2 <- parfib (n - 2)
+              n3 <- (n1 `par` (n2 `seq` (return (n1 + n2 + 1))))
+              return n3
+
+main = do x <- parfib 30; print x

testsuite/tests/ghc-regress/par/par001.stdout

+2692537