Include Arel::Predicates to Arel::Nodes::Function

* 'master' of github.com:rails/arel:
  Make ToSql more thread safe.

Make ToSql more thread safe.

Because the ToSql visitor instance is shared across all threads, there is a
race condition around column types for binary nodes. It's possible, for instance,
to end up with ActiveRecord converting a string value in the final SQL to an
integer during heavy concurrent operations.

InfixOperations should support ordering

should support ordering

Stop calling to_s on aliases, require them to be strings already.

This reverts commit 490d6f98, reversing
changes made to dd07005d.

* 'master' of github.com:rails/arel:
  replace 'LIMIT n' with 'FETCH FIRST n ROWS ONLY' when using ibm_db
  Generate more sqlish queue.

Passing nil in array generates improper SQL

replace 'LIMIT n' with 'FETCH FIRST n ROWS ONLY' when using ibm_db

Add support for specifying order direction on expressions

Conflicts:

	arel.gemspec

Conflicts:

	lib/arel.rb
	lib/arel/attributes/attribute.rb
	lib/arel/nodes/infix_operation.rb
	lib/arel/nodes/named_function.rb

Conflicts:

	lib/arel.rb
	lib/arel/attributes/attribute.rb

1st README example