Removed "<select expression> INTO <destination>" deprication.

This was done after discussions with Igor, Sanja and Bar.

The main reason for removing the deprication was to ensure that MariaDB
is always backward compatible whenever possible.

Other things:
- Added statistics counters, mainly for the feedback plugin.
  - INTO OUTFILE
  - INTO variable
  - If INTO is using the old syntax (end of query)

mysql-test/suite/handler/aria.result

@@ -1540,8 +1540,6 @@ BEGIN
 SELECT 1 FROM t2 INTO @a;
 RETURN 1;
 END|
-Warnings:
-Warning	1287	'<select expression> INTO <destination>;' is deprecated and will be removed in a future release. Please use 'SELECT <select list> INTO <destination> FROM...' instead
 SELECT f1();
 ERROR 42S02: Table 'test.t2' doesn't exist
 CREATE TABLE t1(a INT);

mysql-test/suite/handler/heap.result

@@ -1539,8 +1539,6 @@ BEGIN
 SELECT 1 FROM t2 INTO @a;
 RETURN 1;
 END|
-Warnings:
-Warning	1287	'<select expression> INTO <destination>;' is deprecated and will be removed in a future release. Please use 'SELECT <select list> INTO <destination> FROM...' instead
 SELECT f1();
 ERROR 42S02: Table 'test.t2' doesn't exist
 CREATE TABLE t1(a INT);

mysql-test/suite/handler/innodb.result

@@ -1544,8 +1544,6 @@ BEGIN
 SELECT 1 FROM t2 INTO @a;
 RETURN 1;
 END|
-Warnings:
-Warning	1287	'<select expression> INTO <destination>;' is deprecated and will be removed in a future release. Please use 'SELECT <select list> INTO <destination> FROM...' instead
 SELECT f1();
 ERROR 42S02: Table 'test.t2' doesn't exist
 CREATE TABLE t1(a INT);

mysql-test/suite/handler/myisam.result

@@ -1540,8 +1540,6 @@ BEGIN
 SELECT 1 FROM t2 INTO @a;
 RETURN 1;
 END|
-Warnings:
-Warning	1287	'<select expression> INTO <destination>;' is deprecated and will be removed in a future release. Please use 'SELECT <select list> INTO <destination> FROM...' instead
 SELECT f1();
 ERROR 42S02: Table 'test.t2' doesn't exist
 CREATE TABLE t1(a INT);