The parser accepted an undocumented non-standard synonym of the `AS` keyword in
some parts of the MySQL grammar:

  ... [AS|=] alias ...

To comply with the documentation, the current patch has removed that support in
a few contexts:

1.  LOCK TABLES tbl_name [[AS] alias] ...

2.  HANDLER tbl_name OPEN [[AS] alias]

3a. tbl_name [PARTITION...] [[AS] alias] ...

3b. table_subquery [AS] alias ...

4.  JSON_TABLE(... [AS] alias)

Change-Id: Ie7dd9f007f419968ffbc5875a2b566a318f632ee