bug#44766: valgrind error when using convert() in a subquery

Problem: input and output buffers may be the same 
converting a string to some charset. 
That may lead to wrong results/valgrind warnings.  

Fix: use different buffers.

             warnings after uncompressed_length 
 
UNCOMPRESSED_LENGTH() did not validate its argument. In 
particular, if the argument length was less than 4 bytes, 
an uninitialized memory value was returned as a result. 
 
Since the result of COMPRESS() is either an empty string or 
a 4-byte length prefix followed by compressed data, the bug was 
fixed by ensuring that the argument of UNCOMPRESSED_LENGTH() is 
either an empty string or contains at least 5 bytes (as done in 
UNCOMPRESS()). This is the best we can do to validate input 
without decompressing. 

Change the warning message to 'Statement may not be safe to log in
statement format' to indicate that the decision on whether a
statement is safe or not is heuristic, and we are conservative.

The RAND(N) function where the N is a field of "constant" table
(table of single row) failed with a SIGFPE.

Evaluation of RAND(N) rely on constant status of its argument.
Current server "seeded" random value for each constant argument
only once, in the Item_func_rand::fix_fields method.
Then the server skipped a call to seed_random() in the
Item_func_rand::val_real method for such constant arguments.

However, non-constant state of an argument may be changed
after the call to fix_fields, if an argument is a field of
"constant" table. Thus, pre-initialization of random value
in the fix_fields method is too early.


Initialization of random value by seed_random() has been
removed from Item_func_rand::fix_fields method.
The Item_func_rand::val_real method has been modified to
call seed_random() on the first evaluation of this method
if an argument is a function.

Fix bug in mtr_cases.pm script visible only when InnoDB isn't configured.

Occasionally, if both the partition_pruning
and partition_range tests are run sequentially
against the IBMDB2I engine, the partition_range
test will fail.

Compiler padding on a 64-bit build allowed
garbage data in the hash key used for
caching open iconv descriptors. As a
result, cached descriptors were not found,
and multiple duplicate iconv descriptors
were opened for a single character set.
Eventually, the maximum number of open
iconv descriptors was reached, and further
iconv_open() calls would fail, leading the
storage engine to report incorrectly that
the character set was not supported.

This patch widens the 16-bit members of the
hash key to 32 bits to eliminate compiler
padding. The entire length of the hash key
is now initialized correctly on both 32-bit
and 64-bit builds.

In order to better support the usage of
IBMDB2I tables from within RPG programs,
the storage engine should ensure that the
RCDFMT name is consistent and predictable
for DB2 tables.

This patch appends a "RCDFMT <name>"
clause to the CREATE TABLE statement
that is passed to DB2.  <name> is
generated from the original name of
the table itself. This ensures a
consistent and deterministic mapping
from the original table.

For the sake of simplicity only
the alpha-numeric characters are
preserved when generating the new
name, and these are upper-cased;
other characters are replaced with
an underscore (_). Following DB2
system identifier rules, the name
always begins with an alpha-character
and has a maximum of ten characters.
If no usable characters are found in
the table name, the name X is used.

Details:
Most tests mentioned within the bug report were already fixed.
The test modified here failed in stability (high parallel load) tests.

Details:
1. Take care that disconnects are finished before the test terminates.
2. Correct wrong handling of send/reap in events_stress which caused
   random garbled output
3. Minor beautifying of script code

  It turns out that this test case no longer fails with the discrepancy
  in numbers that was the original cause for disabling this test (and showed
  potential genuine issues with the query cache). Therefore
  this test is being enabled after some minor adjustment of error codes and
  messages.

Details:
1. Add missing "disconnect <session>"
2. Take care that the disconnects are finished when the test terminates
3. Replace error names by error numbers
4. Minor beautifying of script code

 
Field_time::get_time() did not initialize some members of 
MYSQL_TIME which led to valgrind warnings when those members 
were accessed in Protocol_simple::store_time(). 
 
It is unlikely that this bug could result in wrong data 
being returned, since Field_time::get_time() initializes the 
'day' member of MYSQL_TIME to 0, so the value of 'day' 
in Protocol_simple::store_time() would be 0 regardless 
of the values for 'year' and 'month'.

Remove a cast (which shouldn't have got here anyway)
which might lose significant bits beyond 4 GB RAM.