Allow arithmetic operators inside C++ template constructs.
Fixes debbugs #22486.
* lisp/progmodes/cc-langs.el (c-multichar->-op-not->>-regexp): New language
variable.
(c-<>-notable-chars-re): New language variable.
* lisp/progmodes/cc-engine.el (c-forward-<>-arglist-recur): User
c-<>-notable-chars-re in place of the former fixed string in searching for
places to stop and examine.
Use c-multichar->-op-not->>-regexp to check that a found ">" is not part of a
multichar operator in place of the former c->-op-without->-cont-regexp.
Add code to skip forwards over a balanced parenthesized expression.