While equal is symmetric, member is not; in the latter case the
arguments must be a variable and a constant list, in that order.
Reported by Ikumi Keita.
* lisp/emacs-lisp/bytecomp.el (byte-compile--cond-switch-prefix):
Don't treat equality and member predicates in the same way; only
the former are symmetric in their arguments.
* test/lisp/emacs-lisp/bytecomp-tests.el
(byte-opt-testsuite-arith-data): Add test cases.