support multiline eval

you can now evaluate multiline expressions, such as the following:

inc :: Int -> Int
inc n = n   1

import Control.Monad (forM_)

putMany :: (Show a) => [a] -> IO ()
putMany xs = forM_ xs $ \x -> do
    putStrLn $ show x

however, the following limitations still apply:

• you have to select the expression you want to evaluate
  • except if it's a one-line expression
• you can only eval one expression at a time
• all output is printed inline, not on lighttable's console