Adding classes VDec and VDec2_lazy, according to the task description.
This patch removes around 250 duplicate code lines.

This also better matches the package order in downstream, so it makes
it easier to compare upstream and downstream. Also wrap-and-sort.

After this there will be no need to maintain line numbers, as the
extent of the sed deletion will automatically be until next empty line.

- Update package names that had -10.3 to -10.4
- Update conflicts/breaks/replaces of to include now also 10.3,
  just like 10.3 had the same relationship to 10.2
- Remove some old  (<< ${source:Version}) not needed anymore as we
  are not moving files around inside the 10.4 releases (at least yet).
- Ensure all plugins depend on server or client binaries from the same
  release so that they for sure are binary API compatible.

Due to an obvious bug in st_select_lex_unit::reset_distinct() a union
without duplicates of more than 2 selects could return a result set
containing duplicate rows if this union was enclosed in ().

The bug appeares because of the lamely saved list of multiple equalities.
To fix it and_new_conditions_to_optimized_cond() was changed.

- Implementing the task according to the MDEV description.
- Adding a helper class Sec6_add to share the code in type-specific
  branches in Item_func_add_time::get_date().

The problem appears because of the pushdown of a non-pushable condition 'cond'
into the materialized derived table/view. To prevent pushdown a map of
tables that are used in 'cond' should be updated. This call is missing
because of the MDEV-12387 changes. The call is added in the
setup_jtbm_semi_joins() method.

failed

The bug appeared as in MDEV-12387 setup_jtbm_semi_joins() procedure had been
devided into two functions, one called before optimization of WHERE clause
and another after this optimization. When the second function was called for
a degenerated jtbm semi join equalities connecting the subselect and
the parent select were created but invocation of fix_fields() for these
equalities was missing.

Adding new methods:

- virtual void Type_handler::Column_definition_reuse_fix_attributes()
  according to the MDEV description

- virtual uint32 Field::character_octet_length()
  To simplify handling of Column_definition::length for
  TEXT and VARCHAR columns (with and without compression).

The problem occurred because the Spider node was incorrectly handling
timestamp values sent to and received from the data nodes.

The problem has been corrected as follows:
- Added logic to set and maintain the UTC time zone on the data nodes.
  To prevent timestamp ambiguity, it is necessary for the data nodes to use
  a time zone such as UTC which does not have daylight savings time.
- Removed the spider_sync_time_zone configuration variable, which did not
  solve the problem and which interfered with the solution.
- Added logic to convert to the UTC time zone all timestamp values sent to
  and received from the data nodes.  This is done for both unique and
  non-unique timestamp columns.  It is done for WHERE clauses, applying to
  SELECT, UPDATE and DELETE statements, and for UPDATE columns.
- Disabled Spider's use of direct update when any of the columns to update is
  a timestamp column.  This is necessary to prevent false duplicate key value
  errors.
- Added a new test spider.timestamp to thoroughly test Spider's handling of
  timestamp values.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Merged:
  Commit 97cc9d34 on branch bb-10.3-MDEV-16246

Field_varstring::sql_type() did not calculate character length correctly.
Using char_length() instead of the bad code.

The problem occurs on Ubuntu where a Spider package is installed on the system
separately from the MariaDB package.  MariaDB and Spider upgrades leave the
Spider plugin improperly installed.  Spider is present in the mysql.plugin
table but is not present in information_schema.

The problem has been corrected in Spider's installation script.  Logic has
been added to check for Spider entries in both information_schema and
mysql.plugin.  If Spider is present in mysql.plugin but is not present in
information_schema, then Spider is first removed from mysql.plugin.  The
subsequent plugin install of Spider will insert entries in both mysql.plugin
and information_schema.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Cherry-Picked:
  Commit 0897d81 on branch bb-10.3-MDEV-15786

The problem occurs on Ubuntu where a Spider package is installed on the system
separately from the MariaDB package.  MariaDB and Spider upgrades leave the
Spider plugin improperly installed.  Spider is present in the mysql.plugin
table but is not present in information_schema.

The problem has been corrected in Spider's installation script.  Logic has
been added to check for Spider entries in both information_schema and
mysql.plugin.  If Spider is present in mysql.plugin but is not present in
information_schema, then Spider is first removed from mysql.plugin.  The
subsequent plugin install of Spider will insert entries in both mysql.plugin
and information_schema.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Cherry-Picked:
  Commit 0897d81 on branch bb-10.3-MDEV-15786

This helped fix MDEV-16779.

Declare all fields of purge_vcol_info_t private, and add
accessor functions.

During a table-rebuilding operation, the function table_name_parse()
can encounter a table name that starts with #sql. Here is an example
of a failure:

CURRENT_TEST: gcol.innodb_virtual_basic
mysqltest: At line 1204: query 'alter table t drop column d ' failed:
2013: Lost connection to MySQL server during query

Let us just remove these bogus debug assertions.

If the final renaming phase during ALTER TABLE never fails, it
should not do any harm to skip the purge. If it does fail, then
we might end up 'leaking' some delete-marked records in the
indexes on virtual columns of the original table, and these
garbage records would keep consuming space until the indexes are
dropped or the table is successfully rebuilt.

This is a regression caused by the fix of MDEV-15855.

purge_vcol_info_t::set_used(): Add a missing condition.

row_purge_poss_sec(): Invoke set_used() in order to
have !is_first_fetch() when retrying.

This should affect at least rec_printer() output.

Replace pairs of rw_lock_own() calls with
calls to rw_lock_own_flagged().

These calls are only present in debug builds.

There is only one temporary tablespace. Reserving a data member in
each read-write lock object for a Boolean flag seems like a huge waste,
especially because this field was only actually used in debug builds.

LatchDebug::check_order(): Compare to fil_system.temp_space->latch.