Fix EXPLAIN FORMAT=JSON to produce output that's not worse than
the tabular form.

Provide basic info about sorting/grouping done by the queries.

report when a pattern is found
do not abort, but merely report when a pattern is not found

that is, after

  commit dd8f9319
  Author: Sergei Golubchik <serg@mariadb.org>
  Date:   Fri Apr 10 02:36:54 2015 +0200

    be less annoying about sysvar-based table attributes
    do not *always* add them to the create table definition,
    but only when a sysvar value is different from a default.
    also, when adding them - don't quote numbers

dereferencing of the uninitialized pointer bpade->slot
(when compiled without UNIV_DEBUG)

MDEV-7816 ALTER with DROP INDEX and ADD INDEX .. COMMENT='comment2' ignores the new comment

If a flag is supported only for C or C++ - add it to the
corresponding compiler option list. Old behavior was to
add always to both, but only if supported in both.

unportable, use grep

that for some reasons worked on linux, but crashed on windows

this will prevent user from creating tables with ENCRYPTED=OFF

because one is supposed always to use it with innodb-encrypt-tables

and make it a session variable, not global, as any decent
default sysvar for a table attribute should be

instead of manually implenting "default from a sysvar" in the code

do not *always* add them to the create table definition,
but only when a sysvar value is different from a default.

also, when adding them - don't quote numbers

fix sys_var->is_default() method (that was using default_val property
in a global sys_var object to track per-session state):
* move timestamp to a dedicated Sys_var_timestamp class
  (in fact, rename Sys_var_session_special_double to Sys_var_timestamp)
* make session_is_default a virtual method with a special implementation
  for timestamps
* other variables don't have a special behavior for default values
  and can have session_is_default() to be always false.

which is separate from the encryption key version

With changes:

* update tests to pass (new encryption/encryption_key_id syntax).
* not merged the code that makes engine aware of the encryption mode
  (CRYPT_SCHEME_1_CBC, CRYPT_SCHEME_1_CTR, storing it on disk, etc),
  because now the encryption plugin is handling it.
* compression+encryption did not work in either branch before the
  merge - and it does not work after the merge. it might be more
  broken after the merge though - some of that code was not merged.
* page checksumming code was not moved (moving of page checksumming
  from fil_space_encrypt() to fil_space_decrypt was not merged).
* restored deleted lines in buf_page_get_frame(), otherwise
  innodb_scrub test failed.

It used to double-encrypt it, relying on the fact that second
encrypt() call was (like XOR) negating the effect of the
first one.

because of encryption changes - make it beta and let
it mature together with the server

rename to innodb-debug-force-scrubbing

rename to innodb-scrub-log-speed

move remaning defines to my_crypt, add MY_ namespace prefix

with namespace prefixes