Merge pull request #1 from chambart/master

Fixpoint with a stack
This allows widening, plus it has a flexible handling of the callstack.
Removing useless .mli's
Adding counter to main test
Adding all samples to main
Adding cycle test
Merge pull request #2 from chambart/master

Add leveled stacks
Useful functor to manipulate complicated stacks.
Merge branch 'master' of http://github.com/thomasblanc/ocaml-data-analysis
Pierre's functor for stack
Merging module type N and LeveledFunction in stack_types.mli
Merge pull request #3 from chambart/master

Add optionnal narrowing phase
Fixpoint returned graph contains original edge attributes
Test_int is a bit more complex

not completely trivial to prove that resulting y is positive
Fix: distinguish different call sites within the same stack
Fix external functions having inputs included in vertex

And a few more asserts
Add dot generation to main