Small copyedits for doc/lispref

* doc/lispref/display.texi (Scroll Bars):
* doc/lispref/modes.texi (Header Lines): Copyedits.

doc/lispref/ChangeLog

@@ -1,5 +1,8 @@
 2014-10-04  Glenn Morris  <rgm@gnu.org>
 
+	* display.texi (Scroll Bars):
+	* modes.texi (Header Lines): Copyedits.
+
 	* buffers.texi (Buffer List):
 	* display.texi (Image Descriptors, Defining Images):
 	* functions.texi (Core Advising Primitives): Small fixes re @var usage.

doc/lispref/display.texi

@@ -3925,9 +3925,9 @@ bar actually occupies.
 @end defun
 
 @defun window-scroll-bar-width &optional window
-This function returns the width of @var{window}'s vertical scrollbar,
-in pixels.  @var{window} must be a live window.  If @var{window} is
-@code{nil} or omitted, it will be the selected window.
+This function returns the width in pixels of @var{window}'s vertical
+scrollbar.  @var{window} must be a live window, and defaults to the
+selected window.
 @end defun
 
 If you don't specify these values for a window with

doc/lispref/modes.texi

@@ -2221,13 +2221,10 @@ is the same as for @code{mode-line-format} (@pxref{Mode Line Data}).
 It is normally @code{nil}, so that ordinary buffers have no header line.
 @end defvar
 
-The function @code{window-header-line-height} returns the height of
-the header line:
-
 @defun window-header-line-height &optional window
-Return the height of @var{window}'s header line, in pixels.
-@var{window} must be a live window.  If @var{window} is @code{nil} or
-omitted, it will be the selected window.
+This function returns the height in pixels of @var{window}'s header
+line.  @var{window} must be a live window, and defaults to the
+selected window.
 @end defun
 
   A window that is just one line tall never displays a header line.  A