support for consistent braces-plus-semicolon-style

e.g. see this nice example (shortened):

module Data.Graph.Inductive.Graphviz
       (Orient(..), graphviz, graphviz') where
{ import Data.Graph.Inductive.Graph;
   
  data Orient = Portrait
              | Landscape
              deriving (Eq, Show);
   
  graphviz ::
           (Graph g, Show a, Show b) =>
             g a b ->
               String -> (Double, Double) -> (Int, Int) -> Orient -> String;
  graphviz g t (w, h) p@(pw', ph') o
    = let { n = labNodes g;
            e = labEdges g}
        in
        "digraph " ++ t ++ " {\n" ++ "\tmargin = \"0\"\n" ++ "\tpage = \""}

Start with the linked example at plugins/de.ovgu.featureide.examples/featureide_examples/FGL-FH-Haskell/features/GraphViz/Data/Graph/Inductive/Graphviz.hs and inspect the formatter's existing handling of braces and semicolons. Done means the shown Haskell style is accepted and formatted consistently without breaking the surrounding syntax.