WL#8662: Deprecate and remove "Delphi style" column and table syntax

Affects: Server-8.0   —   Status: Complete   —   Priority: Medium

The parser supports old Deplhi style syntax for columns and table names:

* .column_name

* .table_name.column_name

* .table_name

I.e. dot sign followed by the column/table name.

The first syntax (".col_name") and the second one (".table_name.column_name")
doesn't seem to be documented at all.

The third syntax (".tbl_name") is documented at
http://dev.mysql.com/doc/refman/5.7/en/identifier-qualifiers.html :

: The syntax .tbl_name means the table tbl_name in the default database.
: This syntax is accepted for ODBC compatibility because some ODBC programs
: prefix table names with a “.” character.

Conclusion: it would be nice to remove the .column_name syntax in 8.0.

Reasoning: the syntax is undocumented and most likely unused.

**User Documentation**

* https://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-20.html
* https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-2.html
* https://dev.mysql.com/doc/refman/5.7/en/identifier-qualifiers.html
(deprecation notice)
* https://dev.mysql.com/doc/refman/8.0/en/identifier-qualifiers.html (removal of
deprecated syntax)
Functional requirements
=======================

In 8.0
------

* F-1: The ".column_name" syntax should cause a syntax error.

* F-2: The ".table_name.column_name" syntax should cause a syntax error.

* F-3: The ".table_name" syntax should cause a syntax error.


Non-functional requirements
===========================

In 5.7
------

* NF-1: Each ".table_name" syntax in any valid SQL statement should cause a deprecation warning.

* NF-2: Each ".table_name.column_name" syntax in any valid SQL statement should causes a deprecation warning.

* NF-3: Each ".column_name" syntax in any valid SQL statement should cause a deprecation warning.
.column syntax
==============

5.7
---

Output a warning on each `.<column name>` entry in DDL:

    Warning	1287	'.<column>' is deprecated and will be removed in a future release. Please use the column name without a dot prefix instead

8.0
---

Output a syntax error on the 1st .<column name> entry in DDL.


.table syntax
=============


5.7
---

Output a warning on each `.<table name>` entry in DDL:

    Warning	1287	'.<table>' is deprecated and will be removed in a future release. Please use the table name without a dot prefix instead


8.0
---

Nothing to do, has done with WL#8657.