This backend provides very simple mmap functionality, as such backing
malloc & co. It uses dm_phys for dataspaces and log for debug output.

This backend is *not* suited for programs, where memory regions are
freed by other threads than they were allocated, because dm_phys'
ownership management is thread based and not task based.  Until
dm_phys right concept is reworked, please use the buddy_slab_mem
backend for such programs.
