Fix minor corner case bugs in byte compilation and pcase.

Fix minor corner case bugs in byte compilation and pcase.
* lisp/emacs-lisp/byte-opt.el (byte-compile-inline-expand): Don't re-preprocess
functions from byte-compile-function-environment.
* lisp/emacs-lisp/bytecomp.el (byte-compile-constp): Treat #'v as a constant.
(byte-compile-close-variables): Bind byte-compile--outbuffer here...
(byte-compile-from-buffer): ...rather than here.
* lisp/emacs-lisp/pcase.el (pcase--expand): Accept different sets of vars in
different alternative patterns.
(pcase-codegen): Be more careful to preserve identity.
(pcase--u1): Don't forget to mark vars as used.