Minor fix for url_for using hash params

Minor fix for url_for where additional values are (incorrectly) set in
the hash...

Before fix:

options = {:controller => 'projects', :action => 'index'}
url_for(options)
options => {:controller => 'projects', :action => 'index', :host =>
'www.example.com', :protocol => 'http'}

After fix:

options = {:controller => 'projects', :action => 'index'}
url_for(options)
options => {:controller => 'projects', :action => 'index'}

Pull request at:
https://github.com/rails/rails/pull/2497

Thanks,
Andrew