Optimizing net related classes

This pull request contains several commits that optimize net related classes. Mainly header parsing and formatting of net messages. The changes are mostly non-critiical. Commit 3c64846 breaks BC, the commit message explains it's why and how. I think it's worth it.

The attached screenshot shows the xhgui summary, comparing the latest dev branch with the patches proposed here. The benchmark is JSON benchmarks from the TechEmpower framework benchmarks.

![bildschirmfoto 2014-05-06 um 23 14 57](https://cloud.githubusercontent.com/assets/29702/2895734/b68c9234-d563-11e3-9bcc-e8f7a38a93ea.png)