Don't use flycheck until I extend the checker.

The Haskell checker needs extending for optional arguments. I currently
have a tedious hack in setup-flycheck.el but that will not do at all:
it's more cumbersome than useful. Upstream said they will welcome
updates so until I write some, I'm disabling it.
Only set Agda input method the first time around.
mc
Don't let flymake error jumps hijack my keys