[TYPO3-core] FYI: Raised Extbase and Fluid version to 0.9.17

[Sebastian Kurfürst]

Hey,

I just raised Extbase and Fluid versions to 0.9.17. The important
changes are:
- Extbase: Fixed a regression which prevented BE modules with
configuration to work (e.g. Viewhelpertest)
- Fluid: Re-enabled ObjectAccessorPostProcessor which I removed by
accident a few commits before. This re-enables Fluid's built-in XSS
protection.

So, now I hope we are finally ready for beta3 ;)

Greets,
Sebastian