bug#45611: 28.0.50; xterm.c compile anomaly and link failure

[Eli Zaretskii]

> From: William C Doughty III <n2ocm@optonline.net>
> Date: Sat, 02 Jan 2021 07:20:39 -0500
> 
> 
> Looking at the compile output for the master branch,
> it appears that Xrender is not being found or the
> test for it is buggy.
> 
> Needed to manually set HAVE_XRENDER and add -lXrender
> to src/Makefile, after this the make compiles xterm.c
> cleanly and the link for temacs succeeds.

Please show the part of config.log where it tests for Xrender
availability.

Thanks.