Implement caching backend for other opcode caches.
Currently the flow3 caching backend as well as its typo3 backport support the APC opcode cache.
Other populare opcode caches e.g. xcache, eaccelerator also offer the the oportunity to store data the shm.
Since the shm storing api accross different opcode caches just varies a little (mainly naming of put/get functions) it might make sense to create a seperated abstract "opcode cache backend" class and let the actual opcode code cache specific backend inherited from it.
I attached very a rough (and not fully tested) xcache caching backend class i put together by copy and pasting from the typo3 apc cache back end. Just to illustrated the minor difference.