MDEV-14857: problem with 10.2.11 server crashing when executing stored procedure

Counter for select numbering made stored with the statement (before was global)
So now it does have always accurate value which does not depend on
interruption of statement prepare by errors like lack of table in
a view definition.

sql/sql_explain.h

@@ -208,6 +208,9 @@ public:
 
   Explain_select(MEM_ROOT *root, bool is_analyze) : 
   Explain_basic_join(root),
+#ifndef DBUG_OFF
+    select_lex(NULL),
+#endif
     message(NULL),
     having(NULL), having_value(Item::COND_UNDEF),
     using_temporary(false), using_filesort(false),
@@ -222,6 +225,9 @@ public:
   void replace_table(uint idx, Explain_table_access *new_tab);
 
 public:
+#ifndef DBUG_OFF
+  SELECT_LEX *select_lex;
+#endif
   const char *select_type;
 
   /*