std.path review: final version(?)

[Lars T. Kyllingstad]

Since the voting is supposed to start today (not in this thread; dsimcha 
will annouce it), here is the (hopefully) final version of std.path:

  https://github.com/kyllingstad/phobos/blob/std-path/std/path.d
  http://www.kyllingen.net/code/std-path/phobos-prerelease/std_path.html

New commits since the last update (dated 2011-08-03 and 2011-08-04) are 
listed here:

  https://github.com/kyllingstad/phobos/commits/std-path

Highlights:

  - extension() now returns the dot together with the extension
  - The dot is optional in set-/defaultExtension()
  - Removed normalize(), since it simply called buildNormalizedPath()

I kept the longer names for *Extension and *Separator, because

  - I personally like them better; they are clear and consistent
  - Jonathan is the only one who seems to really dislike them
  - There is ample precedent for longish function names in Phobos (see 
std.algorithm, for instance)

-Lars