Generated proxy classes have mixed line endings on Windows

When Doctrine\ORM\Proxy\ProxyFactory generates proxy classes on Windows, it mixes LF an CR/LF line endings. This is causing VCS issues in our mixed Windows/Linux dev team (we keep the proxies under version control for deployment purposes).

This seems to be a regression. It did not happen with Doctrine 2.0.x.

It is caused by the template string in the static property $_proxyClassTemplate using LF, while the string concatenations in the methods use the PHP_EOL constant, which resolves to CR/LF on Windows.

Other code generators like Doctrine\ORM\Tools\EntityGenerator use "\n" instead of PHP_EOL.

I propose to always use "\n" in favour of PHP_EOL. It's easier to implement in this case and every editor/IDE on Windows can handle Unix line endings nowadays.