put_inductive_definition implemented and exposed.

put_inductive_definition implemented and exposed.
It is a very UNSAFE solution to the problem of computing inner-types of
non-debrujined mutual inductive types (whose constructors referes to
the not-yet-defined inductive type block): you can use this function to
add the block to the environment; then you compute the inner-types; and
finally you save the object and register it to the getter.