Rework code to add python procfs files that report probe breakpoint details.

Rework code to add python procfs files that report probe breakpoint details.

* tapset-python.cxx (python_derived_probe_group::emit_kernel_module_init):
  New function.
  (python_derived_probe_group::emit_kernel_module_exit): Ditto.
  (python_derived_probe_group::emit_module_decls): Output procfs probe
  buffer code.
  (python_derived_probe_group::emit_module_init): Emit procfs file init
  code.
  (python_derived_probe_group::emit_module_exit): Emit procfs file exit
  code.
  (python_builder::build): Remove synthetic procfs probes.
* runtime/procfs-probes.c: Add copyright header. Move _stp_procfs_data
  structure definition to procfs-probes.h.
  (_stp_proc_open_file): Only reset the buffer if we've got a read_probe
  function.
  (_stp_proc_read_file): Don't exit if we don't have a read_probe
  function.
* tapset-procfs.cxx (procfs_derived_probe::join_group): Move
  _stp_procfs_data structure definition to procfs-probes.h.
* runtime/procfs-probes.h: New file.
* runtime/python.c: Removed unneeded file.