New feature providing single step functionality to the events subsystem. Includes top-level API, specific implementation for the Xen driver, and example code.
Merge pull request #46 from mfusaro/xen-single-step

Xen single step mem_events
Bugfix - linux/memory.c : linux_pgd_to_pid was attempting to reach task_struct->pid by using pgd_offset (copy-paste bug)
linux/memory.c : Simplify linux_get_taskstruct_addr_from_pid and linux_get_taskstruct_addr_from_pgd, and make sure they return the task_struct address as implied by the function name (previously returned address of the related task_struct->tasks)