lock_sys_t::deadlock_check(): Assume that only lock_sys.wait_mutex
is being held by the caller.

lock_sys_t::rd_lock_try(): New function.

lock_sys_t::cancel(trx_t*): Kill an active transaction that may be
holding a lock.

lock_sys_t::cancel(trx_t*, lock_t*): Cancel a waiting lock request.

lock_trx_handle_wait(): Avoid acquiring mutexes in some cases,
and in never acquire lock_sys.latch in exclusive mode.
This function is only invoked in a semi-consistent read
(locking a clustered index record only if it matches the search condition).
Normally, lock_wait() will take care of lock waits.

lock_wait(): Invoke the new function lock_sys_t::cancel() at the end,
to avoid acquiring exclusive lock_sys.latch.

lock_rec_other_trx_holds_expl(): Use LockGuard instead of LockMutexGuard.

lock_release_autoinc_locks(): Explicitly acquire table->lock_mutex,
in case only a shared lock_sys.latch is being held. Deadlock::report()
will still hold exclusive lock_sys.latch while invoking
lock_cancel_waiting_and_release().

lock_cancel_waiting_and_release(): Acquire trx->mutex in this function,
instead of expecting the caller to do so.

lock_unlock_table_autoinc(): Only acquire shared lock_sys.latch.

lock_table_has_locks(): Do not acquire lock_sys.latch at all.

Deadlock::check_and_resolve(): Only acquire shared lock_sys.latchm
for invoking lock_sys_t::cancel(trx, wait_lock).

innobase_query_caching_table_check_low(),
row_drop_tables_for_mysql_in_background(): Do not acquire lock_sys.latch.