Add pcase-defmacro, as well as `quote' and `app' patterns.

Add pcase-defmacro, as well as `quote' and `app' patterns.
* loadup.el: Increase max-lisp-eval-depth when macroexpanding macroexp.
* emacs-lisp/pcase.el: Allow (F . ARGS) in `app' patterns.
(pcase--funcall, pcase--eval): New functions.
(pcase--u1): Use them for guard, pred, let, and app.
(\`): Use the new feature to generate better code for vector patterns.
* emacs-lisp/pcase.el: Use pcase-defmacro to handle backquote.
(pcase--upat): Remove.
(pcase--macroexpand): Don't hardcode handling of `.
(pcase--split-consp, pcase--split-vector): Remove.
(pcase--split-equal): Disregard ` since it's expanded away.
(pcase--split-member): Optimize for quote rather than for `.
(pcase--split-pred): Optimize for quote rather than for `.
(pcase--u1): Remove handling of ` (and of `or' and `and').
Quote non-selfquoting values when passing them to `eq'.
Drop `app's let-binding if the variable is not used.
(pcase--q1): Remove.
(`): Define as a pattern macro.
* emacs-lisp/pcase.el (pcase--match): New smart-constructor function.
(pcase--expand pcase--q1, pcase--app-subst-match): Use it.
(pcase--macroexpand): Handle self-quoting patterns here, expand them to
quote patterns.
(pcase--split-match): Don't hoist or/and here any more.
(pcase--split-equal): Optimize quote patterns as well as ` patterns.
(pcase--flip): New helper macro.
(pcase--u1): Optimize the memq case directly.
Don't handle neither self-quoting nor and/or patterns any more.
* emacs-lisp/pcase.el (pcase-defmacro): New macro.
(pcase--macroexpand): New function.
(pcase--expand): Use it.
* emacs-lisp/pcase.el (pcase--app-subst-match, pcase--app-subst-rest):
New optimization functions.
(pcase--u1): Add support for `quote' and `app'.
(pcase): Document them in the docstring.