partial backport of r15610 : A new status Unsafe in Interface.

Meant for commands such as Admitted but coqtop v8.4 never uses it.
partial backport of r15610 : Second part

ide_slave is ready to send unsafe values but does not.

This part is backported only to make next backports easier, i'm just lazy
Backport of interface.mli and serialize.ml reworked to avoid copy/paste of types

With this commit the types involved in the protocol between Coq and
Coqide are written once and for all in interface.mli

The benefit of this commit is that changing the protocol is easier:
one changes the types in interface.mli and lets ocamlc spot all the
places that needs to be modified.
This is a necessity if one plays with the protocol very often, like
in my Paral-ITP branch.

This is revision trunk@16438

Conflicts:
	ide/coq.ml
	toplevel/ide_intf.ml
	toplevel/ide_intf.mli
	toplevel/ide_slave.ml
Backport Fix indentation

revision trunk@16450

Conflicts:
	toplevel/interface.mli
Reduce the distance with trunk of Interface and Serialize
Partial backport of Coqide: new feedback mechanism for structured content

This amounts to a new type of message called feedback and defined in
Interface to hold structured data.  Coq sends feedback messages
asynchronously (they are all fetched, like regular messages, together
with the main response to a call) and they are related to a specific
sentence by an id.

It is revision trunk@16451.
Partial Backport of raise UnsafeSuccess -> feedback AddedAxiom

It is revision trunk@16452
Partial Backport of Coqide: Globalization feedback (proof of concept)

In v8.4 Loc.t comes with all Camlp? So the interface uses (int * int).

It is revision trunk@16456
Update CHANGES