replace macrollogy in test suite with constraint kinds

[cartazio]

https://github.com/haskell/vector/blob/master/tests/Tests/Vector.hs#L27-L34

#define COMMON_CONTEXT(a, v) \
VANILLA_CONTEXT(a, v), VECTOR_CONTEXT(a, v)
#define VANILLA_CONTEXT(a, v) \
Eq a, Show a, Arbitrary a, CoArbitrary a, TestData a, Model a ~ a, EqTest a ~ Property
#define VECTOR_CONTEXT(a, v) \
Eq (v a), Show (v a), Arbitrary (v a), CoArbitrary (v a), TestData (v a), Model (v a) ~ [a], EqTest (v a) ~ Property, V.Vector v a

vile stuff, lets kill it!