remove Feature_into_old_syntax

it doesn't provide any information we'll use.
No matter what the value is, we don't remove the non-standard
syntax unless we have to

mysql-test/main/features.result

@@ -11,7 +11,6 @@ Feature_dynamic_columns	0
 Feature_fulltext	0
 Feature_gis	0
 Feature_insert_returning	0
-Feature_into_old_syntax	0
 Feature_into_outfile	0
 Feature_into_variable	0
 Feature_invisible_columns	0
@@ -208,6 +207,5 @@ select @x=@y;
 drop table t1;
 show status like "feature_into_%";
 Variable_name	Value
-Feature_into_old_syntax	2
-Feature_into_outfile	2
+Feature_into_outfile	4
 Feature_into_variable	2

sql/mysqld.cc

@@ -7413,7 +7413,6 @@ SHOW_VAR status_vars[]= {
   {"Feature_fulltext",         (char*) offsetof(STATUS_VAR, feature_fulltext), SHOW_LONG_STATUS},
   {"Feature_gis",              (char*) offsetof(STATUS_VAR, feature_gis), SHOW_LONG_STATUS},
   {"Feature_insert_returning", (char*)offsetof(STATUS_VAR, feature_insert_returning), SHOW_LONG_STATUS},
-  {"Feature_into_old_syntax",  (char*) offsetof(STATUS_VAR, feature_into_old_syntax), SHOW_LONG_STATUS},
   {"Feature_into_outfile",     (char*) offsetof(STATUS_VAR, feature_into_outfile), SHOW_LONG_STATUS},
   {"Feature_into_variable",    (char*) offsetof(STATUS_VAR, feature_into_variable), SHOW_LONG_STATUS},
   {"Feature_invisible_columns",(char*) offsetof(STATUS_VAR, feature_invisible_columns), SHOW_LONG_STATUS},

sql/sql_class.h

@@ -968,7 +968,6 @@ typedef struct system_status_var
   ulong feature_window_functions;   /* +1 when window functions are used */
   ulong feature_into_outfile;       /* +1 when INTO OUTFILE is used */
   ulong feature_into_variable;      /* +1 when INTO VARIABLE is used */
-  ulong feature_into_old_syntax;    /* +1 when INTO is used with old syntax*/
 
   /* From MASTER_GTID_WAIT usage */
   ulong master_gtid_wait_timeouts;          /* Number of timeouts */

sql/sql_yacc.yy

@@ -12503,7 +12503,7 @@ opt_procedure_or_into:
         | into opt_select_lock_type
           {
             $$= $2;
-            status_var_increment(thd->status_var.feature_into_old_syntax);
+            status_var_increment(thd->status_var.feature_into_outfile);
           }
         ;