Fix HAVING queries for PostgreSQL

[sandermarechal]

This should fix the failing unittests under PostgreSQL. I don't have psql myself, but from the description by @l3pp4rd in #298 this should fix the issue. Tested with SQLite and MySQL.

[asm89]

If you go to http://travis-ci.org/ and login with your github account, you should be able to enable the doctrine2 repository. After doing that, travis will run the tests for you on various platforms like here: http://travis-ci.org/#!/doctrine/doctrine2.

Can you check it out? (For this branch you could do -> enable doctrine2 on travis -> force push the branch again.)

[beberlei]

Still fails http://travis-ci.org/#!/doctrine/doctrine2/jobs/852996

You have to do put everything in SELECT into GROUP BY, or make the SELECT simpler. I will try to find a fix, i guess its easier when you have postgresql to test against. Thanks for trying anyways :-)

[l3pp4rd]

yes, it shouldn't be hard to install, the previous error is fixed, now the other one

[sandermarechal]

I never realised that I could put my own fork on Travis as well. Thanks! I fixed it. It's all green now: http://travis-ci.org/#!/sandermarechal/doctrine2

I'll create a new PR