completed definition of stern_brocot_enum; however, there seems to be something wrong with it, as it's not being evaluated.

Signed-off-by: Pepijn Kokke <pepijn.kokke@gmail.com>
created several tasks to help with common coqdoc commands
defined coind, eq, eq_refl, eq_sym and eq_trans for cotrees.

Signed-off-by: Pepijn Kokke <pepijn.kokke@gmail.com>