bug#46509: 28.0.50; Unused static function in xfns.c with GTK2

[Robert Pluim]

>>>>> On Mon, 15 Feb 2021 11:05:59 +0100, martin rudalics <rudalics@gmx.at> 
>>>>> said:

    >> What about this instead:
    martin> Better.  The ChangeLog is slightly excessive.

And ChangeLog entries for changes depending on preprocessor directives
are supposed to put the directives in [ ], eg

commit 97226aacfde717ec48fa8931c870497e089da17b
Author: Paul Eggert <eggert@cs.ucla.edu>
Date:   Mon Jan 4 10:33:43 2021 -0800

    Do not assume Xrender merely because Cairo
    
    Problem reported by Andrea Corallo in:
    https://lists.gnu.org/r/emacs-devel/2021-01/msg00225.html
    * src/xterm.c (x_term_init) [USE_CAIRO && !HAVE_XRENDER]:
    Do not call XRenderQueryExtension.