Don't free the client's selected db (thd->db) when it has been DROPped,
if this is a slave thread; the x_free() was causing a lot
of various bugs in rpl_loaddata_rule_m (garbage characters, segfault, hangs in
other threads).
A small post-merge fix (rli->inside_transaction exists in 4.0 only).


sql/log_event.cc:
  Post-merge fix (rli->inside_transaction existed in 4.0 only)
sql/sql_db.cc:
  Don't free the client's selected db (thd->db) when it has been DROPped,
  if this is a slave thread; the x_free() was causing a lot
  of various bugs in rpl_loaddata_rule_m which does a DROP DATABASE 
  (garbage characters, segfault, hangs in other threads).