Introduce new macros to cover Emacs's new names in cl-lib.el.

Introduce new macros to cover Emacs's new names in cl-lib.el.

This also eliminates `mapcan' warnings in XEmacs.

progmodes/cc-defs.el (c--mapcan-status): new variable to characterise
[X]Emacs versions.
(top-level): Require either 'cl or 'cl-lib, depending on
c--mapcan-status.
Change this back to cc-external-require from an eval-when-compile
require.
(c--mapcan, c--set-difference, c--intersection, c--macroexpand-all)
(c--delete-duplicates): New macros which expand into either old or new
names.
(c-make-keywords-re, c-lang-defconst, c-lang-const) Use the new macros
rather than the old names.

progmodes/cc-engine.el (c-declare-lang-variables): Use c--mapcan rather
than mapcan.

progmodes/cc-fonts.el (c-compose-keywords-list): Use c--mapcan.

progmodes/cc-langs.el (top-level): Require either 'cl or 'cl-lib,
depending on c--mapcan-status.
(c-filter-ops, c-all-op-syntax-tokens, c-assignment-op-regexp)
(c-type-start-kwds, c-prefix-spec-kwds, c-specifier-key)
(c-not-decl-init-keywords, c-not-primitive-type-keywords)
(c-paren-any-kwds, c-<>-sexp-kwds, c-block-stmt-kwds, c-expr-kwds)
(c-decl-block-key, c-keywords, c-keywords-obarray)
(c-regular-keywords-regexp, c-primary-expr-regexp,
c-primary-expr-regexp)
(c-block-prefix-disallowed-chars, c-known-type-key,
c-nonlabel-token-key)
(c-make-init-lang-vars-fun): Use the new macros rather than the old
names.