graphs: style changes

graphs: style changes

* src/graphviz.c (start_graph): Use courier font.
(conclude_red): Use commas to separate attributes. Show the acceptation
as a special reduction, with a blue color and an "Acc" label. Show the
lookahead tokens between square brackets.
(output_red): No longer label default reductions.
* src/print_graph.c (print_core): Refactor spacing, and print an
additional space between a rule's rhs and its lookahead tokens. Also,
capitalize "State".
(print_actions): Style, move a declaration.

Signed-off-by: Akim Demaille <akim@lrde.epita.fr>