First try to complete inference for typeclasses
* Fix an invalid type variable name generation in the type inference engine.
* Fix missing checking that records contain the right fields.
* Fix two negative tests that were rejected for invalid reasons.
Merge branch 'master' of github.com:yurug/mpri13 into inference
+ Solved the local_let_bound case
Conflicts:
	src/elaboration/elaborationEnvironment.mli
	src/elaboration/elaborationExceptions.ml
Merge branch 'master' of github.com:pcouderc/mpri13