* lisp/progmodes/idlw-shell.el: Use lexical-binding

* lisp/progmodes/idlw-shell.el: Use lexical-binding

(idlwave-shell-source-frame): Remove unused var 'frame'.
(idlwave-shell): Remove unused arg 'quick'.
(idlwave-shell-complete-filename, idlwave-shell-edit-default-command-line)
(idlwave-shell-retall, idlwave-shell-closeall): Remove unused arg 'arg'.
(idlwave-shell-move-to-bp): Remove unused var 'got-bp'.
(zmacs-regions): Declare.
(idlwave-shell-update-bp-overlays): Remove unused var 'win'.
(idlwave-shell-delete-expression-overlay)
(idlwave-shell-mouse-nop): Delete function.  Use 'ignore' instead.
(idlwave-shell-delete-output-overlay): Ignore 'ignore' commands rather
than idlwave-shell-mouse-nop commands.
(idlwave-shell-mode-map, idlwave-shell-electric-debug-mode-map):
Move (part of) the initialization into the declaration.
(idlwave-shell-electric-debug-mode-on-hook)
(idlwave-shell-electric-debug-mode-off-hook): Keep them empty, move
code into the minor mode's definition instead.
(idlwave-shell-electric-debug-mode): Don't use advice needlessly.