Minor fixes.

Minor fixes.

(Parameter Access): frame-parameters arg is optional.
modify-frame-parameters handles nil for FRAME.
(Window Frame Parameters): menu-bar-lines and tool-bar-lines
are all-or-nothing for certain toolkits.
Mention parameter wait-for-wm.
(Frames and Windows): In frame-first-window and frame-selected-window
the arg is optional.
(Input Focus): In redirect-frame-focus the second arg is optional.
(Window System Selections): Mention selection type CLIPBOARD.
Mention data-type UTF8_STRING.
Mention numbering of cut buffers.
(Resources): Describe x-resource-name.