TYPO3 Core

Update the caching framework to FLOW3 version 868e073b98

Main changes:
- [!!!][FEATURE] Make cache backends more flexible
This change makes cache backends more flexible. It adds a new
interface "TaggableBackendInterface" and a new "SimpleFileBackend".
The latter does not support tagging but is faster in certain cases
(where with a lot of tags/entries flushing everything is faster than
flushing by tag).

If you have implemented a cache backend and support tagging, you must
  add the "TaggableBackendInterface" to the list of interfaces implemented
  by your backend.

- [BUGFIX] Fix default lifetime use in cache backend

- [FEATURE] Freezable Cache Backend
Introduce a new type of cache backends which supports freezing.
In a frozen state no modifications are allowed and thus enables the
cache implementation to optimize its tasks for speed.

The FileBackend was extended to support freezing.