Add new argument `ignore-line-at-end' to `window-text-pixel-size'

Add new argument `ignore-line-at-end' to `window-text-pixel-size'

* doc/lispref/display.texi (Size of Displayed Text): Update
documentation.
* etc/NEWS: Announce new argument.
* src/xdisp.c (window_text_pixel_size): Allow controlling if
the iterator's ascent and descent will be appended to the
pixel height returned.  All callers changed.
(Fwindow_text_pixel_size): New argument `ignore-line-at-end'.
All callers changed.