fix gcc 8 compiler warnings

There were two newly enabled warnings:
1. cast for a function pointers. Affected sql_analyse.h, mi_write.c
   and ma_write.cc, mf_iocache-t.cc, mysqlbinlog.cc, encryption.cc, etc

2. memcpy/memset of nontrivial structures. Fixed as:
* the warning disabled for InnoDB
* TABLE, TABLE_SHARE, and TABLE_LIST got a new method reset() which
  does the bzero(), which is safe for these classes, but any other
  bzero() will still cause a warning
* Table_scope_and_contents_source_st uses `TABLE_LIST *` (trivial)
  instead of `SQL_I_List<TABLE_LIST>` (not trivial) so it's safe to
  bzero now.
* added casts in debug_sync.cc and sql_select.cc (for JOIN)
* move assignment method for MDL_request instead of memcpy()
* PARTIAL_INDEX_INTERSECT_INFO::init() instead of bzero()
* remove constructor from READ_RECORD() to make it trivial
* replace some memcpy() with c++ copy assignments

sql/sql_show.cc

@@ -6266,7 +6266,7 @@ static int get_schema_views_record(THD *thd, TABLE_LIST *tables,
         {
           TABLE_LIST table_list;
           uint view_access;
-          memset(&table_list, 0, sizeof(table_list));
+          table_list.reset();
           table_list.db= tables->db;
           table_list.table_name= tables->table_name;
           table_list.grant.privilege= thd->col_access;