Er... No. It's an patch file - meaning you need to use it with the patch command (see patch --help).
This patch file requires the source code of xterm for that one file it attempts to patch. This means you need to get the source code of xterm, apply the patch to charproc.c and compile and install xterm manually to use this fix.
Not to leave you completely in the dark, you can attempt to do the following also from the above guide: http://www.davidsimmons.com/soft/xtermhacks/#copynpastenopatch
Note two things though. By default SliTaz doesn't have an .Xresources file, so use .Xdefaults instead. Also .Xdefaults is a hidden file, so make sure pcmanfm is showing hidden files to see and edit it. You may have to logout and back in before the change has any effect though.