Addressed the following issues from the review of the patch:

1. The PERSISTENT FOR clause of the ANALYZE command overrides
the setting of the system variable use_stat_tables: 
with this clause ANALYZE unconditionally collects persistent
statistics.
2. ANALYZE collects persistent statistics only for tables of
the USER category. So it never collects persistent statistics
for system tables.

sql/sql_lex.h

@@ -2452,6 +2452,7 @@ struct LEX: public Query_tables_list
     this command.
   */
   bool parse_vcol_expr;
+  bool with_persistent_for_clause; // uses PERSISTENT FOR clause (in ANALYZE)
 
   enum SSL_type ssl_type;			/* defined in violite.h */
   enum enum_duplicates duplicates;