xtrabackup_copy_log(), xtrabackup_copy_logfile():
Change the Boolean parameter to an enum, with the values
COPY_FIRST, COPY_ONLINE, COPY_LAST.

xtrabackup_copy_log(): Return the latest scanned LSN,
which may be less than the last copied LSN. Remove some
dead code that was duplicating some logic that in 10.2
has been moved to log_group_read_log_seg().

log_copying_thread(): Correct the termination condition.

stop_backup_threads(): Shut down the threads that were
created during backup.

Use GET_STR instead of GET_STR_ALLOC, so that the memory will
cannot be leaked. For some reason, calling my_cleanup_options()
on xb_server_options or xb_client_options would not work.

This reduces the probability having output of external utilities
(e.g mariabackup) truncated.

MDEV-12445 : Rocksdb does not shutdown worker threads and aborts in memleak check on server shutdown

Disable memory leak check in debug server, if rocksdb is loaded.
There is some subtle bug somewhere in 3rd party code we cannot
do much about.

The bug is manifested as follows

Rocksdb does not shutdown worker threads, when plugin is shut down. Thus
OS does not unload the library since there are some active threads using
this library's code. Thus global destructors in the library do not run,
and there is still some memory allocated when server exits.

The workaround disables server's memory leak check, if rocksdb engine was
loaded.

Use thd_query_safe() to read query from a different connection.

Replace S_IREAD, S_IWRITE and S_IEXEC with more modern equivalents.
Fixes building for Android.

Since MariaDB 10.2.2, temporary table metadata is not written
to the InnoDB data dictionary tables. Therefore,
the DICT_TF2_TEMPORARY flag cannot be set in SYS_TABLES,
except if there exist orphan temporary tables that were created
before MariaDB 10.2.2.

trx_resurrect_table_locks(): Do not skip temporary tables.
If a resurrect transaction modified a temporary table that was
created before MariaDB 10.2.2, that table would be treated
internally as a persistent table. It is safer to resurrect
locks than to skip the table, because the table would be modified
on transaction rollback.

buf_flush_page_cleaner_coordinator: In the first loop, use an
appropriate termination condition, waiting for !recv_writer_thread_active.

logs_empty_and_mark_files_at_shutdown(): Signal recv_sys->flush_start
in case the recv_writer_thread was never started, or
buf_flush_page_cleaner_coordinator failed to notice its termination.

innobase_start_or_create_for_mysql(): Remove a redundant, unreachable
condition, and properly release resources when aborting startup due to
recv_sys->found_corrupt_log.

for compatibility with MySQL, add 'JSON' as an alias for 'TEXT'

with -DPLUGIN_PARTITION=NO and -DPLUGIN_PERFSCHEMA=NO

Fix INFORMATION_SCHEMA.COLUMNS.COLUMN_DEFAULT to be standard-compliant,
but keep SHOW COLUMNS backward-compatibly unchanged.

if we don't need to print field's table name,
we surely don't need to print field's db name either

Use the correct target name when querying libmariadb.so dependencies.
Filter out linker options (no-undefined and the version script)

remove double-initialization of MYSQL structure

remove ANSI_QUOTES when generating partition syntax for frm

Remove now-unused part_func_string and subpart_func_string
from partition_info.

don't print partitioning expression as it was entered by the user,
use Item::print() according to the sql_mode and sql_quote_show_create

Don't write to a temporary file, use String.
Remove strange one-liner "helpers", use String methods.
Don't use current_thd, don't allocate memory for 1-byte strings, etc.

don't do auditing if thd is NULL.

Collaterals:
* copy-paste bugs server_audit.c
* uninitialized user field when thd in NULL

when opening 10.1- table that has virtual columns:

1. don't error out if it has vcols over autoinc columns.
   just issue a warning.
2. set vcol type properly
3. in innodb: use table->s->stored_fields instead of table->s->fields,
   because that's what was stored in innodb data dictionary

and
MDEV-13144 regexp on views - crashed mariadb server

implement Item_func_regex::build_clone()

use correct type for Alter_inplace_info flags.

MDEV-11930 Unexpected ER_ERROR_EVALUATING_EXPRESSION warning upon dropping database with a bad table

DBUG_EXECUTE_IF was wrong, it used my_error, but didn't do error=1.

It's not clear what it was actually testing, what it was supposed
to be testing, and what it has to do with bug#43138, so I removed it.

CRYPTO_set_mem_functions() works only until the first allocation is done:
* remove the second CRYPTO_set_mem_functions() call
* check whether the first CRYPTO_set_mem_functions() call worked
* stricter memory checks (==1, not >1, etc)
* as coc_malloc cannot be removed, make the counter a bit cheaper
* only do the check for OpenSSL 1.1 (because of OpenSSL 1.0 bug)

the array only needs to be reallocated if it's smaller
than needed. Being larger is ok.

also: remove a duplicated check (merge error)

don't use thd->query_id check in background purge threads
(it doesn't work, because thd->query_id is never incremented there)
instead use thd->open_tables directly, there can be only one table
there anyway, and this is the table opened by this purge thread.

cannot use unireg_abort() until mutexes are initialized.

On Windows, when tmpdir is not writable, there are only messages
like this:

2017-07-05 14:04:25 3860 [ERROR] InnoDB: Unable to create temporary file; errno: 0

On other platforms, there would be two messages for each failure:

2017-07-05 17:23:02 140436573771648 [ERROR] mysqld: Can't create/write to file '/dev/null/nonexistent/ibaajU4U' (Errcode: 20 "Not a directory")
2017-07-05 17:23:02 140436573771648 [ERROR] InnoDB: Unable to create temporary file; errno: 20

Interval function makes use of Item_row. Item_row did not correctly mark
with_window_func flag according to its arguments. Fix it by making
Item_row aware of this flag.

When using innodb_page_size=16k, InnoDB tables
that were created in MariaDB 10.1.0 to 10.1.20 with
PAGE_COMPRESSED=1 and
PAGE_COMPRESSION_LEVEL=2 or PAGE_COMPRESSION_LEVEL=3
would fail to load.

fsp_flags_is_valid(): When using innodb_page_size=16k, use a
more strict check for .ibd files, with the assumption that
nobody would try to use different-page-size files.