Adding "const" qualifier to Item::cols(), and to the "Item *cmp" parameter to Type_handler::make_const_item_for_comparison()

This gives better performance, as excludes handler-by-type lookup.

This is a join patch fixing these two bugs:
MDEV-12560 Wrong data type for SELECT NULL UNION SELECT Point(1,1)
MDEV-12665 Hybrid functions do not preserve geometry type

Port of mysql changeset by Georgi Kodinov <Georgi.Kodinov@Oracle.com>:

    Bug #34325 : --add-drop-trigger option for mysqldump

    Implemented the --add-drop-trigger option to prepend each
    CREATE TRIGGER in the dump file with DROP TRIGGER.
    The option is off by default. Added a test case.

Fixing result set metadata for Item_int to match type_handler(),
i.e. MYSQL_TYPE_LONG for small numbers and MYSQL_TYPE_LONGLONG for big numbers.

The new 10.2 has log-slow-admin-statements ON but log-slow-queries OFF,
thus  there is no reason for a warning about it(the change was "by design")

Making sql_yacc.yy close to sql_yacc_ora.yy:

1. Adding struct sp_cursor_name_and_offset into %union
2. Adding field_type_numeric, field_type_string,  field_type_lob,
   field_type_temporal, field_type_misc
3. Adding keyword_sp_data_type and keyword_sp_not_data_type
4. Removing "opt_savepoint". Moving this grammar to "rollback" instead.
   This fixes one shift/reduce conflict.
5. Minor indentation cleanup.

The usage of windows functions when all tables were optimized away
by min/max optimization were not supported. As result a result,
the queries that used window functions with min/max aggregation
over the whole table returned wrong result sets.
The patch fixed this problem.

Removing duplication:
- fix_length_and_dec()
- tmp_value
- lpad_str, rpad_str -> pad_str

(from: http://buildbot.askmonty.org/buildbot/builders/p8-rhel6-bintar/builds/820/steps/test/logs/stdio)

Errors like the following indicate a potential endian storage issue:

rocksdb.rocksdb_range                    w1 [ fail ]
        Test ended at 2017-04-27 18:56:11

CURRENT_TEST: rocksdb.rocksdb_range
--- /home/buildbot/maria-slave/p8-rhel6-bintar/build/storage/rocksdb/mysql-test/rocksdb/r/rocksdb_range.result	2017-04-27 17:41:27.740050347 -0400
+++ /home/buildbot/maria-slave/p8-rhel6-bintar/build/storage/rocksdb/mysql-test/rocksdb/r/rocksdb_range.reject	2017-04-27 18:56:11.230050346 -0400
@@ -25,15 +25,15 @@
 select * from t2 force index (a) where a=0;
 pk	a	b
 0	0	0
-1	0	1
-2	0	2
-3	0	3
-4	0	4
-5	0	5
-6	0	6
-7	0	7
-8	0	8
-9	0	9
+16777216	0	1
+33554432	0	2
+50331648	0	3
+67108864	0	4
+83886080	0	5
+100663296	0	6
+117440512	0	7
+134217728	0	8
+150994944	0	9
 # The rest are for code coverage:
 explain
 select * from t2 force index (a) where a=2;
@@ -41,23 +41,23 @@
 1	SIMPLE	t2	ref	a	a	4	const	#
 select * from t2 force index (a) where a=2;
 pk	a	b
-20	2	20
-21	2	21
-22	2	22
-23	2	23
-24	2	24
-25	2	25
-26	2	26
-27	2	27
-28	2	28
-29	2	29
+335544320	2	20
+352321536	2	21
+369098752	2	22
+385875968	2	23
+402653184	2	24
+419430400	2	25
+436207616	2	26
+452984832	2	27
+469762048	2	28
+486539264	2	29
 explain
 select * from t2 force index (a) where a=3 and pk=33;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	const	a	a	8	const,const	#
 select * from t2 force index (a) where a=3 and pk=33;
 pk	a	b
-33	3	33
+553648128	3	33
 select * from t2 force index (a) where a=99 and pk=99;
 pk	a	b
 select * from t2 force index (a) where a=0 and pk=0;
...
Signed-off-by: Daniel Black <daniel.black@au.ibm.com>

        Flags are wrongly set for MBR_CONTAINS/MBR_WITHIN functions.

MDEV-12363 Assertion `0' failed in Type_handler_string_result::make_sort_key(uchar*, Item*, const SORT_FIELD_ATTR*, Sort_param*).

        maybe_null wasn't properly set for Item_json_func_keys.

json_find_path.

        The ..[0] path can be treated wrong on second json_find_path
        call.

JSON_SEARCH with variables.

        Wrong index for the tmp_paths array in
        Item_func_json_search::val_str.

MDEV-12657 A few tests fail in build-bot on Windows after changing Field::field_name and Item::name to LEX_CSTRING

Merged fix into 10.2.

post-fix for 0b52b28b

* restore EXPLAIN output
* remove redundant code

MDEV-12293 Assertion `table->no_keyread || !table->covering_keys.is_set(tab->index) || table->file->keyread == tab->index' failed

sometimes the optimizer starts a keyread on some index
and later (but before any actual index accesses) changes
it to a keyread on a different index

Recompile it for embedded.
Test it for embedded.
Promote it to Gamma

innochecksum uses global variables. great, let's use them all the
way down, instead of passing them as arguments to innodb internals,
conditionally modifying function prototypes with #ifdefs

The bug happened when the specification of a recursive CTE had
no recursive references at the top level of the specification.
In this case the regular processing of derived table references
of the select containing a non-recursive reference to this
recursive CTE misses handling the specification unit.
At the preparation stage any non-recursive reference to a
recursive CTE must be handled after the preparation of the
specification unit for this CTE. So we have to force this
preparation when regular handling of derived tables does not
do it.