patch 8.2.1281: the "trailing characters" error can be hard to understand

Problem:    The "trailing characters" error can be hard to understand.
Solution:   Add the trailing characters to the message.
diff --git a/src/ex_eval.c b/src/ex_eval.c
index 3fdc208..f0ffaff 100644
--- a/src/ex_eval.c
+++ b/src/ex_eval.c
@@ -1588,7 +1588,7 @@
 	    if (end != NULL && *end != NUL
 				      && !ends_excmd2(end, skipwhite(end + 1)))
 	    {
-		emsg(_(e_trailing));
+		semsg(_(e_trailing_arg), end);
 		return;
 	    }