patch 8.0.0793: using wrong terminal name for terminal window

Problem:    Using wrong terminal name for terminal window.
Solution:   When 'term' starts with "xterm" use it for $TERM in a terminal
            window.

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    793,
 /**/
     792,
 /**/