Storage/FilterCrypt: Remove hardcoded data unit size of 512 bytes and introduce interface to query the size from the generic layer
Storage/VD: Cleanup VD plugin handling. One shared object can now support an arbitrary number of image backends instead of just one like before
vdifs-internal.h: Fix copy and paste error
header (C) fixes
Storage/Backends: async/sync I/O unification, remove separate entries for sync and async I/O callbacks, remove unused code
Storage: Next step in the sync/async I/O unification, change all calls to pfnRead/pfnWrite/pfnFlush to pfnAsyncRead/pfnAsyncWrite/pfnFlush
Storage: Preparations for the sync/async I/O unification
VD: Interface cleanup. Merge the two involved structures (generic interface descriptor and callback table) into one, remove the duplicated interface wrappers in the backends and move the interface definitions into separate headers separating public and private interfaces.