Enabled multiline in ghci and customized multiline prompt

ghci

@@ -1,5 +1,7 @@
 :set prompt "λ > "
+:set prompt2 "λ² > "
 {- :set -Wall -}
+:set +m
 
 let ghciEscapeShellArg arg = "'" ++ concatMap (\c -> if c == '\'' then "'\"'\"'" else [c]) arg ++ "'"