Adding tests for the bug.

A contributed patch by Andrei Boros (SCA signed).
- Fixing locale definition file
- Adding tests

Problem: using null microsecond part in a WHERE condition 
(e.g. WHERE date_time_field <= "YYYY-MM-DD HH:MM:SS.0000") 
may lead to wrong results due to improper DATETIMEs 
comparison in some cases.

Fix: comparing DATETIMEs as strings we must trim trailing 0's
in such cases.


mysql-test/r/innodb_mysql.result:
  Fix for bug#47963: Wrong results when index is used
    - test result.
mysql-test/t/innodb_mysql.test:
  Fix for bug#47963: Wrong results when index is used
    - test case.
sql/item.cc:
  Fix for bug#47963: Wrong results when index is used
    - comparing DATETIMEs as strings we must trim trailing 0's in the 
  microsecond part to ensure
  'YYYY-MM-DD HH:MM:SS.000' == 'YYYY-MM-DD HH:MM:SS'

 
The problem was in incorrect handling of predicates involving 
NULL as a constant value by the range optimizer. 
 
For example, when creating a SEL_ARG node from a condition of 
the form "field < const" (which would normally result in the 
"NULL < field < const" SEL_ARG),  the special case when "const" 
is NULL was not taken into account, so "NULL < field < NULL" 
was produced for the "field < NULL" condition. 
 
As a result, SEL_ARG structures of this form could not be 
further optimized which in turn could lead to incorrectly 
constructed SEL_ARG trees. In particular, code assuming SEL_ARG 
structures to always form a sequence of ordered disjoint 
intervals could enter an infinite loop under some 
circumstances. 
 
Fixed by changing get_mm_leaf() so that for any sargable 
predicate except "<=>" involving NULL as a constant, "empty" 
SEL_ARG is returned, since such a predicate is always false. 

mysql-test/r/partition_pruning.result:
  Fixed a broken test case.
mysql-test/r/range.result:
  Added a test case for bug #47123.
mysql-test/r/subselect.result:
  Fixed a broken test cases.
mysql-test/t/range.test:
  Added a test case for bug #47123.
sql/opt_range.cc:
  Fixed get_mm_leaf() so that for any sargable
  predicate except "<=>" involving NULL as a constant, "empty"
  SEL_ARG is returned, since such a predicate is always false.

Use "#ifdef", not plain "#if".

            view that has Group By
      
When SELECT'ing from a view that mentions another,
materialized, view, access was being denied. The issue was
resolved by lifting a special case which avoided such access
checking in check_single_table_access. In the past, this was
necessary since if such a check were performed, the error
message would be downgraded to a warning in the case of SHOW
CREATE VIEW. The downgrading of errors was meant to handle
only that scenario, but could not distinguish the two as it
read only the error messages.
      
The special case was needed in the fix of bug no 36086.
Before that, views were confused with derived tables.
      
After bug no 35996 was fixed, the manipulation of errors
during SHOW CREATE VIEW execution is not dependent on the
actual error messages in the queue, it rather looks at the
actual cause of the error and takes appropriate
action. Hence the aforementioned special case is now
superfluous and the bug is fixed.


mysql-test/r/view_grant.result:
  Bug#46019: Test result.
mysql-test/t/view_grant.test:
  Bug#46019: Test case.
sql/sql_parse.cc:
  Bug#46019: fix.

      
Implemented the server infrastructure for the fix:

1. Added a function LEX_STRING *thd_query_string(THD) to return
a LEX_STRING structure instead of char *.
This is the function that must be called in innodb instead of 
thd_query()

2. Did some encapsulation in THD : aggregated thd_query and 
thd_query_length into a LEX_STRING and made accessor and mutator 
methods for easy code updating. 

3. Updated the server code to use the new methods where applicable.

Temporary tables may set join->group to 0 even though there is 
grouping. Also need to test if sum_func_count>0 when JOIN::exec() 
decides whether to present results in a grouped manner.

sql/sql_select.cc:
  Temporary tables may set join->group to 0 even though there is 
  grouping. Also need to test if sum_func_count>0 when JOIN::exec() 
  decides whether to present results in a grouped manner.

            columns without where/group
                     
Simple SELECT with implicit grouping used to return many rows if
the query was ordered by the aggregated column in the SELECT
list. This was incorrect because queries with implicit grouping
should only return a single record.
                              
The problem was that when JOIN:exec() decided if execution needed
to handle grouping, it was assumed that sum_func_count==0 meant
that there were no aggregate functions in the query. This
assumption was not correct in JOIN::exec() because the aggregate
functions might have been optimized away during JOIN::optimize().
                  
The reason why queries without ordering behaved correctly was
that sum_func_count is only recalculated if the optimizer chooses
to use temporary tables (which it does in the ordered case).
Hence, non-ordered queries were correctly treated as grouped.
                  
The fix for this bug was to remove the assumption that
sum_func_count==0 means that there is no need for grouping. This
was done by introducing variable "bool implicit_grouping" in the
JOIN object.

mysql-test/r/func_group.result:
  Add test for BUG#47280
mysql-test/t/func_group.test:
  Add test for BUG#47280
sql/opt_sum.cc:
  Improve comment for opt_sum_query()
sql/sql_class.h:
  Add comment for variables in TMP_TABLE_PARAM
sql/sql_select.cc:
  Introduce and use variable implicit_grouping instead of (!group_list && sum_func_count) in places that need to test if grouping is required. Also added comments for: optimization of aggregate fields for implicitly grouped queries  (JOIN::optimize) and choice of end_select method (JOIN::execute)
sql/sql_select.h:
  Add variable implicit_grouping, which will be TRUE for queries that contain aggregate functions but no GROUP BY clause. Also added comment to sort_and_group variable.