obj: change void* to uint64_t in alloc and free
obj: make data buffer persistent
obj: fix logging alloc

The alloc operation should be logged before allocating memory.
obj: fix names of on-abort functions

Make names of on-abort functions consistent with on-commit functions.
Merge pull request #16 from ldorau/obj-fix-names-of-on-abort-functions

obj: fix names of on-abort functions
Merge pull request #17 from ldorau/obj-make-data-persistent-fix-logging-alloc

obj: make data buffer persistent and fix logging alloc