CC Mode: Amend C-M-a/e to handle lambda function in C++ arglist

CC Mode: Amend C-M-a/e to handle lambda function in C++ arglist

* lisp/progmodes/cc-cmds.el (c-where-wrt-brace-construct): Reformulate latter
part such that the least enclosing braces and parentheses are used when
determining containment in such.  c-beginning-of-decl-1 has been superseded
by list movement and syntactic whitespace movement.
(c-backward-to-nth-BOF-{): Work on least enclosing parens rather than parens
at any level when moving back to an opening brace.
(c-forward-to-nth-EOF-\;-or-}): Work on least enclosing parens, as above.
Move the correction of point when in a "function trailer" to after the main
loop, correcting a minor bug.