Fixed PR13055 by getting procfs probes working on 3.1 kernels.

Fixed PR13055 by getting procfs probes working on 3.1 kernels.

* runtime/procfs.c (_stp_rmdir_proc_module): Fix problem where
  '/proc/systemtap' wasn't getting removed correctly.
  (_stp_mkdir_proc_module): Add support for kernels where neither
  path_lookup() or kern_path_parent() are exported (such as the 3.1
  kernels).
* buildrun.cxx (compile_pass): Convert compile test for kern_path_parent()
  to an export test.  Add exports tests for path_lookup() and
  vfs_path_lookup().
* runtime/autoconf-kern-path-parent.c: Removed.