This also solves a name clash with the extension order of CMRAs.

Before, it failed when these tactics were invoked with persistent
hypotheses. The new behavior is more convenient when using these
tactics to build other tactics.

This comment mostly addresses issue #34.

There are still some issues:

- For iLöb we can write `iLöb (x1 .. xn) as "IH"` to revert x1 .. xn
  before performing Löb induction. An analogue notation for iInduction
  results in parsing conflicts.
- The names of the induction hypotheses in the Coq intro pattern are
  ignored. Instead, when using `iInduction x as pat "IH"` the induction
  hypotheses are given fresh names starting with "IH". The problem here
  is that the names in the introduction pattern are idents, whereas the
  induction hypotheses are inserted into the proof mode context, and thus
  need to have strings as names.

This closes issue 32.

This solves issue 33.

Make the elements of gset persistent by changing the core



See merge request !11

This makes the typeclass mechanism able to use instances like [Is_true X -> Blah], where X reduces to X.

We need to change the core of X from ∅ to X to make elements of gset persistent.

Before this commit, given "HP" : P and "H" : P -★ Q with Q persistent, one
could write:

  iSpecialize ("H" with "#HP")

to eliminate the wand in "H" while keeping the resource "HP". The lemma:

  own_valid : own γ x ⊢ ✓ x

was the prototypical example where this pattern (using the #) was used.

However, the pattern was too limited. For example, given "H" : P₁ -★ P₂ -★ Q",
one could not write iSpecialize ("H" with "#HP₁") because P₂ -★ Q is not
persistent, even when Q is.

So, instead, this commit introduces the following tactic:

  iSpecialize pm_trm as #

which allows one to eliminate implications and wands while being able to use
all hypotheses to prove the premises, as well as being able to use all
hypotheses to prove the resulting goal.

In the case of iDestruct, we now check whether all branches of the introduction
pattern start with an `#` (moving the hypothesis to the persistent context) or
`%` (moving the hypothesis to the pure Coq context). If this is the case, we
allow one to use all hypotheses for proving the premises, as well as for proving
the resulting goal.

rvs is (classically) equivalent to a kind of double negation

Proofs showing that rvs is equivalent to a kind of step-indexed double negation modality under classical axioms. For now, placed in algebra/double_negation.v until the new directory structure is finalized.

cc: @jung @robbertkrebbers 

See merge request !8

Define disjointness of namespaces in terms of masks.\n\nThe proofs are made simpler and some lemmas get more general.