* (c-constant-symbol): New function which supersedes c-const-symbol.

* (c-constant-symbol): New function which supersedes c-const-symbol.
During a customize-.. call it enables an element of (e.g.)
c-hanging-braces alist to have its name displayed, even when the default
value of c-h-b etc. doesn't include the elemnt.  Replace uses of the old
function by the new.

* progmodes/cc-vars.el (c-hanging-braces-alist): Remove the obscure
non-working fragment ":value c-".