New branch feature/named-lambdas.

[Alan Mackenzie]

Hello, Emacs.

I've just committed the first version of branch feature/named-lambdas.

This will output the @dfn{defining symbol} of any anonymous functions in
backtraces.

For example, in

    (defun foo ()
      "foo doc string"
      (lambda (bar) "lambda doc string" (car bar)))

M-: (funcall (foo) 'baz) will produce this backtrace:

Debugger entered--Lisp error: (wrong-type-argument listp baz)
  car(baz)
  {foo} #f(compiled-function (bar) "lambda doc string" #<bytecode 
-0x105933d3d8452e4e>)(baz)  <=============================
  funcall({foo} #f(compiled-function (bar) "lambda doc string" #<bytecode 
-0x105933d3d8452e4e>) baz)
  (progn (funcall (foo) 'baz))
  elisp--eval-last-sexp(nil)
  eval-last-sexp(nil)
  funcall-interactively(eval-last-sexp nil)
  command-execute(eval-last-sexp)

..  Note the {foo} on the third and fourth lines.  This is (usually) the
defun where the lambda was defined, and is helpful in locating its
source code.

This was achieved by adding an extra defining-symbol field to each of
the three forms of function (interpreted, byte-compiled,
native-compiled).  It is indended that this version of Emacs will
continue to handle functions compiled without this enhancement.

-- 
Alan Mackenzie (Nuremberg, Germany).