This patch:- added support for the fake HP simulator PMU. Most of the
  code provided by Ian Wienand. Allows a kernel compiled for
  the simulator and with CONFIG_PERFMON enabled to boot.

- cleaned up all CTX_*() macros for the context state changes.

- relaxed constraint for system-wide session by allowing all
  task with access to the context's file descriptor to
  manipulate the context as long as they run on the CPU the
  context is attached to.