Fix a race condition that was introduced in debug code by MDEV-14638.

lock_rec_other_trx_holds_expl(): After acquiring the lock_sys->mutex,
check if the transaction might have been committed. Otherwise,
the assertion in the trx_sys.rw_trx_hash traversal callback could fail.

In a Ubuntu Xenial build environment, the compiler identified as
g++-5.real (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
seems to be emitting incorrect code for the compilation unit
trx0rec.cc, triggering a bogus-looking AddressSanitizer report
of an invalid read of something in the function trx_undo_rec_get_pars().
This is potentially affecting any larger tests where the InnoDB
purge subsystem is being exercised.

When the optimization level of trx0rec.cc is limited to -O1, no
bogus failure is being reported. With -O2 or -O3, a lot of things
seemed to be inlined in the function, and the disassembly of the
generated code did not make sense to me.

Item_cond::eval_not_null_tables(): Use Item::eval_const_cond(),
just like Item_cond::fix_fields().

This inconsistency was found while merging to 10.3, where the
Microsoft compiler is configured to report an error for comparing
longlong to bool.

MDEV-18869 Assertion `!((field)->vcol_info && (field)->stored_in_db())' failed in innodb_col_no upon altering table with system versioning

WITH/WITHOUT SYSTEM VERSIONING is not supported for generated columns
at parser level (see definition of field_def rule).

Before MDEV-12113 (MariaDB Server 10.1.25), on shutdown InnoDB would write
the current LSN to the first page of each file of the system tablespace.
This is incompatible with MariaDB's InnoDB table encryption, because
encryption repurposed the field for an encryption key ID and checksum.

buf_page_is_corrupted(): For the InnoDB system tablespace, skip
FIL_PAGE_FILE_FLUSH_LSN when checking if a page is all zero,
because the first page of each file in the system tablespace can
contain nonzero bytes in the field.

By applying 7bd258c4.

unfortunately, the year 2038 problem prevented me from pushing
the deadline even further into the future.

btr_cur_compress_recommendation(): Backport a change from 10.3.

This is a follow-up to commit 1bd98154.

The test case for reproducing MDEV-14126 demonstrates that InnoDB can
end up with an index tree where a non-leaf page has only one child page.

The test case innodb.innodb_bug14676111 demonstrates that such pages
are sometimes unavoidable, because InnoDB does not implement any sort
of B-tree rotation.

But, there is no reason to allow a root page with only one child page.

btr_cur_node_ptr_delete(): Replaces btr_node_ptr_delete().

btr_page_get_father(): Declare globally.

btr_discard_only_page_on_level(): Declare with ATTRIBUTE_COLD.
It turns out that this function is not covered by the
innodb.innodb_bug14676111 test case after all.

btr_discard_page(): If the root page ends up having only one child
page, shrink the tree by invoking btr_lift_page_up().

This is follow-up to commit 1bd98154.

Backport some changes to B-tree page accessor functions from 10.3,
including changing page_get_n_recs() to return uint16_t.

If an index page becomes empty, btr_page_empty() should be called.

The predicate page_is_root(), which was added in MariaDB Server 10.2.2,
is based on a wrong assumption.

Under some circumstances, InnoDB can transform B-trees into a degenerate
state where a non-leaf page has no sibling pages. Because of this,
we cannot assume that a page that has no siblings is the root page.
This bug will be tracked as MDEV-19022.

Because of the bug that may affect many InnoDB data files, we must remove
and replace the wrong predicate. Using the wrong predicate can cause
corruption. A leaf page is not allowed to be empty except if it is the
root page, and the entire table is empty.

MariaDB before MDEV-5800 in version 10.2.2 did not support
indexed virtual columns. Non-persistent virtual columns were
hidden from storage engines. Only starting with MDEV-5800, InnoDB
would create internal metadata on virtual columns.

Similar to what was done in MDEV-18084 and MDEV-18960, we adjust two more
code paths for the old tables.

ha_innobase::build_template(): Do not invoke
dict_index_contains_col_or_prefix() for virtual columns if InnoDB
does not store the metadata.

innobase_build_col_map(): Relax an assertion about the number of columns.

ha_innobase::omits_virtual_cols(): Renamed from omits_virtual_cols().

Adding tests to cover how SEQUENCE related statements work in combination
with the slow log configuration commands.

new location for CPackRPM.cmake

found by @marko