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

invoke plugin methods directly

* no --encryption-algorithm option anymore
* encrypt/decrypt methods in the encryption plugin
* ecnrypt/decrypt methods in the encryption_km service
* file_km plugin has --file-key-management-encryption-algorithm
* debug_km always uses aes_cbc
* example_km changes between aes_cbc and aes_ecb for different key versions

because it's going to do more than just key management

only those tests should be disabled in suite.pm that
cannot be disabled from mysqltest files (e.g. when the
server is started with a special command-line option -
unknown option will abort the server before mysqltest
will start its checks).

only one encryption key lookup in most cases instead of three
(has_key, get_key_size, get_key).

numerous issues fixed:
* buffer overflows
* error conditions aren't checked (crash if file doesn't exist)
* accessing random unallocated memory
* hard-coded password
* arbitrary hard-coded key id limit
* incomprehensible error messages (for key_id == 0 it reported
  "The key could not be initialized", for syntax errors the message was
  "Wrong match of the keyID, see the template", for a key id
  larger than hard-coded limit the message was "No asked key", and there
  was an error "Is comment" for a comment).
* tons of small mallocs, many are freed few lines down in the code
* malloc(N) and new char[N] are used both, even in the same function
* redundant memory copies
* pcre - "I can solve it with regular expressions" - with incorrect regexes
* parser context stored in a singleton
* keys are stored as strings and are strlen-ed and hex2bin-ed on every
  get_key() request
* lots of useless code (e.g. sprintf instead of a pointer assignment,
  checking of the file length to read a part of it in a fixed buffer,
  multiplying by sizeof(char) in many places, etc)
* this list is not exhaustive

not an address of some arbitrarily chosen symbol;
not when plugin is successfully loaded (which means - no info
  when plugin->init failed);

in particular, "innodb.innodb-page_encryption,xtradb" should
select these three tests:

innodb.innodb-page_encryption 'cbc,xtradb' [ pass ]  35563
innodb.innodb-page_encryption 'ctr,xtradb' [ pass ]  36858
innodb.innodb-page_encryption 'ecb,xtradb' [ pass ]  36741

and deselect all innodb_plugin tests. This was not the case, because
the %test_combs hash was destructively modified in the loop

* my_aes.h doesn't compile without my_global.h
* typo in a comment
* redundant condition
* if encryption plugin fails, there's no encryption_key_manager
  at plugin deinit time
* encryption plugin tests must run when plugin.so is present,
  not when a plugin is active (otherwise the test will be skipped
  when plugin fails to initialize).

for temporary Aria tables. It can use a faster BLOCK_RECORD

now IVs are always handled internally

and simplify Item_func_aes_encrypt/decrypt

to: different key lengths

Step 5:
-- Rename encryption_key -> encryption_key_id
-- Remove unnecessary code
-- Fix few bugs found
-- Fix test cases and results files

Step 4:
-- Review fixes
-- Rename pages_page_* to pages_*
-- Remove unnecessary code

Step 3:

-- Make encrytion_algorithm changeable by SUPER
-- Remove AES_ECB method from encryption_algorithms
-- Support AES method change by storing used method on InnoDB/XtraDB objects
-- Store used AES method to crypt_data as different crypt types
-- Store used AES method to redo/undo logs and checkpoint
-- Store used AES method on every encrypted page after key_version
-- Add test