Add -D ecso-verbose

[dpomier]

Debug printings can only be triggered from OCaml sources at the moment but should instead be triggered through defines to make it simpler, this would allow debugging without re-compiling the plugin. Maybe the context-specific ones could be triggered via metadata too?

There are currently 5 of them which can be changed separetely:

• [ ] gl_debug_mutations from EcsoAnalyzer.global
• [ ] ctx_debug_archetype_eq from EcsoContext.t
• [ ] ctx_debug_gen from EcsoContext.t with the values no_debugging, simple_debugging and full_debugging
• [ ] the run function of the plugin in ecso.ml defines a let print_ctxs = false in
• [ ] and LocalFlow have a hard coded let print_debug = false too.