This approach is originally by Robbert

This patch was created using

  find -name *.v | xargs -L 1 awk -i inplace '{from = 0} /^From/{ from = 1; ever_from = 1} { if (from == 0 && seen == 0 && ever_from == 1) { print "Set Default Proof Using \"Type*\"."; seen = 1 } }1 '

and some minor manual editing

This fixes the following issue by JH Jourdan:

  The fact of including uPred_[...] in the module uPred (in base_logic.v),
  implies that typeclasses instances are declared twice. Once in module
  uPred and once in module uPred_[...]. This has the unfortunate
  consequence that it has to backtrack to both instances each time the
  first one fails, making failure of type class search for e.g.
  PersistentP potentially exponential.

  Goal ((□ ∀ (x1 x2 x3 x4 x5: nat), True -∗ True) -∗ True : iProp Σ).
    Time iIntros "#H".
    Undo.
    Remove Hints uPred_derived.forall_persistent : typeclass_instances.
    Time iIntros "#H".

Thanks to Jason Gross @ Coq club for suggesting this fix.

Using this new definition we can express being contractive using a
Proper. This has the following advantages:

- It makes it easier to state that a function with multiple arguments
  is contractive (in all or some arguments).
- A solve_contractive tactic can be implemented by extending the
  solve_proper tactic.

This removes Ralf's hack of using later_car, which is not function in the logic.

Thanks to Aleš for suggesting this.

    The idea on magic wand is to use it for curried lemmas and use ⊢ for uncurried lemmas.

Use COFEs only for the recursive domain equation solver

The old choice for ★ was a arbitrary: the precedence of the ASCII asterisk *
was fixed at a wrong level in Coq, so we had to pick another symbol. The ★ was
a random choice from a unicode chart.

The new symbol ∗ (as proposed by David Swasey) corresponds better to
conventional practise and matches the symbol we use on paper.