Lazily print backtrace frame local variables

Instead of printing the local variables for all frames when the
backtrace buffer is created, print them when they are first made
visible.  Add a prefix argument to backtrace-toggle-locals to toggle
local variables display for the entire buffer.
* lisp/emacs-lisp/backtrace.el (backtrace-view): Mention
:show-locals in docstring.
(backtrace-get-section-end): Remove function.
(backtrace-toggle-locals): Add prefix argument.
(backtrace--with-output-variables): Move before first use.
(backtrace--set-frame-locals-visible): New function.
(backtrace--set-locals-visible-overlay): New function.
(backtrace--set-locals-visible): Remove function.
(backtrace-toggle-feature): Remove TODO comment.
(backtrace--print-locals): Skip printing the locals if they are not
visible.

0 files changed, 0 insertions, 0 deletions