CC Mode: Fix an enum intro being parsed as defun-block-intro

CC Mode: Fix an enum intro being parsed as defun-block-intro

* lisp/progmodes/cc-engine.el (c-inside-bracelist-p): Return a bufpos rather
than t for the enum case.
(c-add-stmt-syntax, c-guess-continued-construct): Replace
c-looking-at-or-maybe-in-bracelist by c-inside-bracelist-p, since the former
does not recognize enum brace lists, but the latter does.

* lisp/progmodes/cc-fonts.el (c-get-fontification-context): Replace
c-looking-at-or-maybe-in-bracelist by c-inside-bracelist-p.