for class Item_func_trim. 
For 4.1 it caused wrong output for EXPLAIN EXTENDED commands
if expressions with the TRIM function of two arguments were used.
For 5.0 it caused an error message when trying to select
from a view with the TRIM function of two arguments.
This unexpected error message was due to the fact that the
print method for the class Item_func_trim was inherited from
the class Item_func. Yet the TRIM function does not take a list
of its arguments. Rather it takes the arguments in the form:
  [{BOTH | LEADING | TRAILING} [remstr] FROM] str) |
  [remstr FROM] str

The implementation of the method Item_func_reverse::val_str
for the REVERSE function modified the argument of the function.
This led to wrong results for expressions that contained
REVERSE(ref) if ref occurred somewhere else in the expressions.

argument can lead to a wrong result.

md5() and sha() functions treat their arguments as case sensitive strings.
But when they are compared their arguments were compared as a case
insensitive strings which leads to two functions with different arguments
and thus different results to being identical. This can lead to a wrong
decision made in the range optimizer and thus lead to a wrong result set.

Item_func_md5::fix_length_and_dec() and Item_func_sha::fix_length_and_dec()
functions now set binary collation on their arguments.

load_file() string-function should return NULL rather than throw an error if
the file doesn't exist, as per the manual.

  BUG #11104 
      Took out the offset-=delimiter_length-1 out of the for loop. It was causing
      basically this: 
      select substring_index('the king of the the hill', 'the', -2) to not work.
      The first iteration, offset would be initialised to 24, then strstr would 
      point at 'the king of the the* hill' ('*'means right before the 
      character following), returning a offset of 16. The for loop would then 
      decrement offset by two (3 - 1), to 14, now pointing at 
      "the king of th*e the hill", _skipping_ past the 'e' in the second to last
      'the', and therefore strstr would never have a chance of matching the 
      second to last 'the', then moving on to the 'the' at the begginning of the 
      string!
      In a nutshell, offset was being decremented by too great a value, preventing
      the second to last 'the' from being ever found, hence the result of 
      'king of the the hill' from the query that is reported in the bug report
func_str.test:
  BUG #11104
  Added tests to make sure fix addresses issues in original bug report
func_str.result:
  BUG #11104 
  New results for new tests

needed to be fixed in earlier versions)
Fixed the iteration of how substrings are handled with negative indexes in 
SUBSTRING_INDEX

client via mysql_fetch_fields(). (Bug #11311)

  added out of range handling

  Added test cases for bug #11469.
item_strfunc.h:
  Fixed bug #11469: wrong implementation of the not_null_tables
  method for CONCAT_WS.

  Added a test case for bug #10124.
sql_select.h, item_subselect.cc, sql_select.cc:
  Fixed bug #10124.
  The copy method of the store_key classes can return
  STORE_KEY_OK=0, STORE_KEY_FATAL=1, STORE_KEY_CONV=2 now.
field.cc:
  Fixed bug #10124.
  When ussuing a warning the store methods return 2 instead of 1 now.

in some cases, because "charset(x) = 'string'" was considered
as "x is not null" due to incorrect not_null_tables().

not always correct for NULL values.
Now they always result a non NULL value even
the argument is NULL. It is more usefull for 
debugging purposes.

  Correction after manual merge.

  Added a test case for bug #8669.
item_strfunc.cc:
  Fixed bug #8669.
  Function AES_DECRYPT can return NULL value.

  fixing test results accordingly.
func_system.test:
  New test that illegal mix of collations does not happen anymore.
item_strfunc.h:
    safe_charset_converter() was added for system constants.
item_strfunc.cc:
  safe_charset_converter() was added for system constants.
item_func.cc, item.h, item.cc:
  Bug#8291: Illegal collation mix with USER() function.
  After discussion with PeterG and Serge, a new coercibility
  level for "system constants" was introduced, between
  COERRIBLE and IMPLICIT. Thus:
  SELECT col1 = USER() FROM t1; - is done according to col1 collation.
  SELECT 'string' = USER(); - is done according to USER() collation.
  At the same time, "nagg" and "strong" members were removed as unused.
item_create.cc:
  Version is a system constant too.

  Added a test case for bug #7751.
item_strfunc.cc:
  Fixed bug #7751.
  The function Item_func_conv::val_str did not update
  the unsigned_flag value.

incorrect results when the input was a constant across a multi-row SELECT
statement. (Bug #8248)

  bug#7839 ncorrect collation for char(ascii('a'))

The fix checks if the trim string argument is NULL. If so, the standard
mandates that the function result must be also NULL.

expression involving LEFT() function is used in GROUP BY
field.

  This test was moved into func_group.

Also, Item_sum_hybrid->charset was removed as redundant,
and switched to use collation.collation instead.

Some bigger code changes was necessary becasue of the multi-table-update and the new HANDLER code