readlink `/proc/self/exe` returns absolute path
readlink on `/proc/self/exe` should return an absolute path.

Under Parrot, when the access path of readlink system call is /proc/self/exe,
Parrot will call pfs_process_lookup(pid) to obtain the pfs_process struct and
store the file name referred by /proc/self/exe into target->name.  What we need
to do is ensure the target->name to be absolute path.

Fixes #348.

* ccl/pull/349/head:
  readlink `/proc/self/exe` returns absolute path