Improve error message for faulty usage of "inc" and "dec"

client/mysqltest.c:
  Improve error messages for "inc" and "dec"
mysql-test/r/mysqltest.result:
  Update test result

client/mysqltest.c

@@ -1360,9 +1360,9 @@ int do_modify_var(struct st_query *query,
   const char *p= query->first_argument;
   VAR* v;
   if (!*p)
-    die("Missing arguments to %.*s", query->first_word_len, query->query);
+    die("Missing argument to %.*s", query->first_word_len, query->query);
   if (*p != '$')
-    die("First argument to %.*s must be a variable (start with $)",
+    die("The argument to %.*s must be a variable (start with $)",
         query->first_word_len, query->query);
   v= var_get(p, &p, 1, 0);
   switch (operator) {
@@ -1373,7 +1373,7 @@ int do_modify_var(struct st_query *query,
     v->int_val++;
     break;
   default:
-    die("Invalid operator to do_operator");
+    die("Invalid operator to do_modify_var");
     break;
   }
   v->int_dirty= 1;

mysql-test/r/mysqltest.result

@@ -305,8 +305,8 @@ mysqltest: At line 1: Invalid argument to real_sleep "abc"
 101
 hej
 1
-mysqltest: At line 1: Missing arguments to inc
-mysqltest: At line 1: First argument to inc must be a variable (start with $)
+mysqltest: At line 1: Missing argument to inc
+mysqltest: At line 1: The argument to inc must be a variable (start with $)
 mysqltest: At line 1: End of line junk detected: "1000"
 4
 4
@@ -315,8 +315,8 @@ mysqltest: At line 1: End of line junk detected: "1000"
 99
 hej
 -1
-mysqltest: At line 1: Missing arguments to dec
-mysqltest: At line 1: First argument to dec must be a variable (start with $)
+mysqltest: At line 1: Missing argument to dec
+mysqltest: At line 1: The argument to dec must be a variable (start with $)
 mysqltest: At line 1: End of line junk detected: "1000"
 mysqltest: At line 1: Missing arguments to system, nothing to do!
 mysqltest: At line 1: Missing arguments to system, nothing to do!