Removing LEX::interval_list, as it's not used since parser cleanups

made in 227510e0.
We now use lex->last_field->interval_list directly instead.

sql/sql_lex.cc

@@ -2151,7 +2151,6 @@ void st_select_lex::init_select()
   in_sum_expr= with_wild= 0;
   options= 0;
   sql_cache= SQL_CACHE_UNSPECIFIED;
-  interval_list.empty();
   ftfunc_list_alloc.empty();
   inner_sum_func_list= 0;
   ftfunc_list= &ftfunc_list_alloc;

sql/sql_lex.h

@@ -788,7 +788,6 @@ class st_select_lex: public st_select_lex_node
   Group_list_ptrs        *group_list_ptrs;
 
   List<Item>          item_list;  /* list of fields & expressions */
-  List<String>        interval_list;
   bool	              is_item_list_lookup;
   /* 
     Usualy it is pointer to ftfunc_list_alloc, but in union used to create fake