* lisp/emacs-lisp/map.el (map-let): New macro.
(map--make-pcase-bindings, map--make-pcase-patterns): New functions.
* test/automated/map-tests.el: New test for `map-let'.
Since a map is not a data structure but a concept, adding information
about the possible types of maps can be useful information.
* lisp/emacs-lisp/map.el: Add documentation about the type of MAP to
each public function.
* lisp/emacs-lisp/map.el (map-elt): If map is an alist and key is
found but its associated value is nil, do not return the default
value.
* test/automated/map-tests.el: Add a regression test.
* lisp/emacs-lisp/map.el (map-delete): When map is an array, check if
the key is present to avoid signaling an error.
* test/automated/map-tests.el: Add a test for deleting non-existing
keys from maps.
* lisp/emacs-lisp/map.el (map-elt): Do not use `ignore-errors' when
doing a lookup in arrays, but check the boundaries of the array
instead.
* test/automated/map-tests.el: Adds a test for `map-elt' with arrays
and a negative integer as key.
