Add a new ``-X perf`` Python command line option as well as
:func:`sys.activate_stack_trampoline` and :func:`sys.deactivate_stack_trampoline`
function in the :mod:`sys` module that allows to set/unset the interpreter in a
way that the Linux ``perf`` profiler can detect Python calls. The new
:func:`sys.is_stack_trampoline_active` function allows to query the state of the
perf trampoline. Design by Pablo Galindo. Patch by Pablo Galindo and Christian Heimes
with contributions from Gregory P. Smith [Google] and Mark Shannon.
