relocate.cc: Rewrite relocation algorithm.

relocate.cc: Rewrite relocation algorithm.

Following the recently added documentation, this implementation should be
much easier to follow.

This patch also contains the following commits:

* flower/file-name.cc: Better handling of `.` and `..` components.

  Update tests.

* running.itely: Document relocation.

  Note that the described relocation algorithm doesn't reflect reality; it
  will be implemented in a forthcoming commit.

* main.cc, relocate.cc: Minor code clean-up.