[GH-371] set permissions as expected by composer.phar update

This issue is created automatically through a Github pull request on behalf of robocoder:

Url: https://github.com/doctrine/doctrine2/pull/371

Message:

I'm guessing the executable permissions were removed from these files recently.

composer.json copies the following scripts (i.e., "bin": ["bin/doctrine", "bin/doctrine.php"], ) to the vendor/bin folder.

When running composer.phar update, and doctrine/orm is to be updated, composer fails because these two scripts have been chmod'd to be executable.