Provide persistent window parameters.

Provide persistent window parameters.

* window.c (Vwindow_persistent_parameters): New variable.
(Fset_window_configuration, save_window_save): Handle persistent
window parameters.

* window.el (window-state-ignored-parameters): Remove variable.
(window--state-get-1): Rename argument MARKERS to IGNORE.
Handle persistent window parameters.  Make copy of clone-of
parameter only if requested.  (Bug#10348)
(window--state-put-2): Install a window parameter only if it has
a non-nil value or an existing parameter shall be overwritten.

* windows.texi (Window Configurations, Window Parameters):
Describe persistent window parameters.