Static disabled plugins|engines and dynamic plugins which installed but disabled
are not visible in I_S PLUGINS|ENGINES tables because they are not stored into
global plugin array.
The fix: add such plugins|engines to plugin array with PLUGIN_IS_DISABLED status.
I_S.ENGINES 'Transactions', 'XA', 'Savepoints' fields have NULL value in this case.

Detail:
- Choose the solution that was already in place (before last fix)
  for 6.0
- minor cleanup in comments

Related to operator precedence and associativity.
Make the expressions as explicit as possible.

Addition of hander function was_semi_consistent_read

The test 
1. did not verify that CREATE FUNCTION shall fails in a case of active binlog
   and @@log_bin_trust_function_creators is zero if there is no DETERMINISTIC qualifier
   and super user privilege;
2. contained an explit warning on that CREATE FUNCTION actually succeeded whereas
   it was supposed to fail;
3. did not demand the bin-log be set ON even though it has contained the opt file
   explictily setting the name for the binlog file.
      
Fixed 1-3 with modifying the test accordingly.

            IF(..., CAST(longtext AS UNSIGNED), signed_val)
            (was: LEFT JOIN on inline view crashes server)

Select from a LONGTEXT column wrapped with an expression
like "IF(..., CAST(longtext_column AS UNSIGNED), smth_signed)"
failed an assertion or crashed the server. IFNULL function was
affected too.

LONGTEXT column item has a maximum length of 32^2-1 bytes,
at the same time this is a maximum possible length of any
MySQL item. CAST(longtext_column AS UNSIGNED) returns some
unsigned numeric result of length 32^2-1, so the result of
IF/IFNULL function of this number and some other signed number
will have text length of (32^2-1)+1=32^2 (one byte for the
minus sign) - there is integer overflow, and the length is
equal to zero. That caused assert/crash.

CAST AS UNSIGNED function has been modified to limit maximal
length of resulting number to 67 (maximal length of DECIMAL
and two characters for minus sign and dot).

The test explicitly warned on existence of a bug in its 27th part.
The expected values of prepare and commit counters changed, corrected, by
fixes to bug#40221.
Notice, that binlog does not have to register for a statement with
the statement binlog-format because the statement rollback does not need
to do anything in that mode. It's not so with the ROW format which was
bug#40221 concern.

Fixed with correcting the expected values of the mentioned counters and
explained that with comments in the test.

            IF(..., CAST(longtext AS UNSIGNED), signed_val)
            (was: LEFT JOIN on inline view crashes server)

Select from a LONGTEXT column wrapped with an expression
like "IF(..., CAST(longtext_column AS UNSIGNED), smth_signed)"
failed an assertion or crashed the server. IFNULL function was
affected too.

LONGTEXT column item has a maximum length of 32^2-1 bytes,
at the same time this is a maximum possible length of any
MySQL item. CAST(longtext_column AS UNSIGNED) returns some
unsigned numeric result of length 32^2-1, so the result of
IF/IFNULL function of this number and some other signed number
will have text length of (32^2-1)+1=32^2 (one byte for the
minus sign) - there is integer overflow, and the length is
equal to zero. That caused assert/crash.

The bug has been fixed by the same solution as in the CASE
function implementation.

Fix parsing of mysql client commands, especially in relation to
single-line comments when --comments was specified.

This is a little tricky, because we need to allow single-line
comments in the middle of statements, but we don't want to allow
client commands in the middle of statements. So in
comment-preservation mode, we go ahead and send single-line
comments to the server immediately when we encounter them on their
own. 

This is still slightly flawed, in that it does not handle a
single-line comment with leading spaces, followed by a client-side
command when --comment has been enabled. But this isn't a new
problem, and it is quite an edge condition. Fixing it would require
a more extensive overall of how the mysql client parses commands. 

Merge from 5.0-bugteam. Additional fix for unused ret variable warning.

BUG#38826

Added KEY_BLOCK_SIZE option to I_S.TABLES.CREATE_OPTIONS field

Bug#37671 crash on prepared statement + cursor + geometry + too many open files!
if mysql_execute_command() returns error then free materialized_cursor object.
is_rnd_inited is added to satisfy rnd_end() assertion
(handler may be uninitialized in some cases)

Removed values with more than 15 significant digits from the test case. Results of 
reading/printing such values using system library functions depend on implementation 
and thus are not portable.