* window.c (Vwindow_point_insertion_type): New var.

* window.c (Vwindow_point_insertion_type): New var.
(set_window_buffer): Use it.
(syms_of_window): Init and export it to Lisp.
* progmodes/compile.el (compilation-mode):
Set window-point-insertion-type.
(compilation-filter): Don't use insert-before-markers any more.
* emacs-lisp/trace.el (trace-make-advice):
Set window-point-insertion-type in the trace buffer.
* startup.el (normal-top-level): Set window-point-insertion-type in
*Messages*.
* net/telnet.el (telnet-mode): Set window-point-insertion-type.
(telnet-filter): Don't use insert-before-markers any more.
* comint.el (comint-mode): Set window-point-insertion-type.
(comint-output-filter): Don't use insert-before-markers any more.
* button.el (make-text-button): Allow `start' to be a string.