Merge commits done at master into rails4

This pull request merges several commits at master branch into rails4 branch.

- This pull request/commits has been created as follows.

```ruby
- checkout current rails4 branch
`git checkout rails4`

- create a topic branch to merge 
`git checkout -b rails4_merges_master_2nd`

- merges master branch commits into rails4_merges_master branch
`git merge master`

- push rails4_merges_master to origin at github
`git push origin rails4_merges_master`
```

- Conflict resolutions

```ruby
Conflicts:
	lib/active_record/connection_adapters/oracle_enhanced_base_ext.rb
	lib/active_record/connection_adapters/oracle_enhanced_schema_dumper.rb
	spec/active_record/connection_adapters/oracle_enhanced_schema_dump_spec.rb

Conflict resolutions:
	lib/active_record/connection_adapters/oracle_enhanced_base_ext.rb
    - `0fdeb26f` and `f50aa48` have been merged to `lib/active_record/connection_adapters/oracle_enhanced_model.rb`

	lib/active_record/connection_adapters/oracle_enhanced_schema_dumper.rb
    - `e897d63` needs ruby 1.9 hash style

  spec/active_record/connection_adapters/oracle_enhanced_schema_dump_spec.rb
    - `e897d63` needs ruby 1.9 hash style
```