The following things have been changed in this revision:

* We now give a small step semantics for expressions. The denotational semantics
  only works for side-effect free expressions.
* Dynamically allocated memory through alloc and free is now supported.
* The following expressions are added: assignment, function call, unary
  operators, conditional, alloc, and free.
* Some customary induction schemes for expressions are proven.
* The axiomatic semantics (and its interpretation) have been changed in order
  to deal with non-deterministic expressions.
* We have added inversion schemes based on small inversions for the operational
  semantics. Inversions using these schemes are much faster.
* We improved the statement preservation proof of the operational semantics.
* We now use a variant of SsReflect's [by] and [done], instead of Coq's [now]
  and [easy]. The [done] tactic is much faster as it does not perform
  inversions.
* Add theory, definitions and notations on vectors.
* Separate theory on contexts.
* Change [Arguments] declarations to ensure better unfolding.

* Introduce a type class and notation for disjointness.
* Define unions of finite maps (a lot of theory has still to be
  moved from memory to fin_maps).
* Prove the Hoare rule for function calls with arguments.
* Prove the Hoare rule to add sets of functions.
* Some additional theory on lifting of assertions.

improve some definitions, simplify some proofs.

The main changes are:

* Function calls in the operational semantics
* Mutually recursive function calls in the axiomatic semantics
* A general definition of the interpretation of the axiomatic semantics  so as
  to improve reusability (useful for function calls, and also for expressions
  in future versions)
* Type classes for stack independent, memory independent, and memory extensible
  assertions, and a lot of instances to automatically derive these properties.
* Many additional lemmas on the memory and more robust tactics to simplify
  goals involving is_free and mem_disjoint
* Proof of preservation of statements in the smallstep semantics

* Some new tactics: feed, feed destruct, feed inversion, etc...
* More robust tactic scripts using bullets and structured scripts
* Truncate most lines at 80 characters

Before, it just ensured that whenever one can split up the memory
into two parts before running the program, the framing part can
be split off when the program is finished. Now it also ensure that
it can be split off at any moment during the execution of the
program.

When we extend to non-deterministic expressions/sequence points we
certainly need this for the Hoare judgment for expressions, as C
allows evaluation of them to interleave. However, for consistency,
and further extensions, it is nice to have this property for
statements too.