need performance testing as part of unit tests

[andygill]

We need

• How fast is the compiler?
• How fast is the generated code?

as well as correctness checks.

[andygill]

I've drafted this up, but not check it in yet.

data Timings = Timings
        { compileTime :: !NominalDiffTime        -- how long spent compiling
        , sendTime    :: !NominalDiffTime        -- how long spent sending
        , waitTime    :: !NominalDiffTime        -- how long spent waiting for a response
        }
        deriving Show

[andygill]

We now have a way or printing to the test in question line, so we just need to reset and read the timings now.

[andygill]

We have this now. We need larger examples than fib 30, though.