Adding a axiomatic testing framework library to help test Hugs and GHC
libraries.

Here is the example for the test of concat.

test_concat = testRules "concat" [
	do (xss :: [[ALPHA]]) <- var "xss"
	   concat xss <==> foldr (++) [] xss
	]

xss here ranges over various rendering of list of list,
including bottom and lists containing bottom.

<==> uses a small piece of compiler/interpreter specifics to
allow testing for

	error "" ... <==> ... error "" ===> Pass