field.cc
- Fixed warning about overlapping memory copy (backport from 10.0)

Item_subselect.cc
- Fixed core dump in main.view
- Problem was that thd->lex->current_select->master_unit()->item was not set, which caused crash in maxr_as_dependent

sql/mysqld.cc
- Got error on shutdown as we where freeing mutex before all THD objects was freed
  (~THD uses some mutex). Fixed by during shutdown freeing THD inside mutex.

sql/log.cc
- log_space_lock and LOCK_log where locked in inconsistenly. Fixed by not having a log_space_lock around purge_logs.

sql/slave.cc
- Remove unnecessary log_space_lock
- Move cond_broadcast inside lock to ensure we don't miss the signal