Rails 2.3.9

Prepare for Rails 2.3.9. Release 2.3.9.pre gems.

Add .yardopts so YARD can document Rails

mysql db defaults to mysql2 gem

fix bad logic in determining if in rails app subdir

Signed-off-by: David Heinemeier Hansson <[email protected]>

Merge branch 'master' of github.com:rails/rails

SQLite: forward compatibility with future driver releases

[rails#4633]

Signed-off-by: Jeremy Kemper <[email protected]>

2.3.7 release: fix rails_xss compatibility

2.3.6 release

Merge branch 'master' of github.com:rails/rails