- Fixed bug in default compiler plus those of postgresql, mysql, and
mssql to ensure that any literal SQL expression values are
rendered directly as literals, instead of as bound parameters,
within a CREATE INDEX statement. [ticket:2742]
- don't need expression_as_ddl(); literal_binds and include_table
take care of this functionality.

Conflicts:
	lib/sqlalchemy/sql/util.py
Parenthesis will be applied to a compound SQL expression as
rendered in the column list of a CREATE INDEX statement.
[ticket:2742]