This fixes MySQL Bug#80788 in MariaDB 10.2.5.

When I made the InnoDB crash recovery more robust by implementing
WL#7142, I also introduced an extra redo log scan pass that can be
shortened.

This fix will slightly extend the InnoDB redo log format that I
introduced in MySQL 5.7.9 by writing the start LSN of the MLOG_CHECKPOINT
mini-transaction to the end of the log checkpoint page, so that recovery
can jump straight to it without scanning all the preceding redo log.

LOG_CHECKPOINT_END_LSN: At the end of the checkpoint page, the start LSN
of the MLOG_CHECKPOINT mini-transaction. Previously, these bytes were
written as 0.

log_write_checkpoint_info(), log_group_checkpoint(): Add the parameter
end_lsn for writing LOG_CHECKPOINT_END_LSN.

log_checkpoint(): Remember the LSN at which the MLOG_CHECKPOINT
mini-transaction is starting (or at which the redo log ends on
shutdown).

recv_init_crash_recovery(): Remove.

recv_group_scan_log_recs(): Add the parameter checkpoint_lsn.

recv_recovery_from_checkpoint_start(): Read LOG_CHECKPOINT_END_LSN
and if it is set, start the first scan from it instead of the
checkpoint LSN. Improve some messages and remove bogus assertions.

recv_parse_log_recs(): Do not skip DBUG_PRINT("ib_log") for some
file-level redo log records.

recv_parse_or_apply_log_rec_body(): If we have not parsed all redo
log between the checkpoint and the corresponding MLOG_CHECKPOINT
record, defer the check for MLOG_FILE_DELETE or MLOG_FILE_NAME records
to recv_init_crash_recovery_spaces().

recv_init_crash_recovery_spaces(): Refuse recovery if
MLOG_FILE_NAME or MLOG_FILE_DELETE records are missing.