I made std.time for Phobos, please review my code.

[SHOO]

I make std.time module for Phobos. This module provides Time, Span,
Clock, StopWatch and some utility functions for time operation.
I hope combine this module to Phobos instead of std.date.

download is here:
	http://j.mp/95aS1K (== http://dusers.dip.jp/ ... /time.d)
	http://j.mp/9p5DDu (patch for Phobos's trunk r1481)
	http://ideone.com/eiQ19 (for code view)

Besides, is there the necessary function? (This module lacks the
daylight saving time handling, because of a lack of my understanding.)


I talk about the process that reached making...

Tango is great library for D1. I am Tango user and I am indebted to
Tango well. But Tango has some probrems.

- Tango's license is BSD lisence or AFL. This license is incompatible to
Phobos's Boost license.
- The specification is disregarded, for example Object.dispose and string.
- Tango supports only D1
- In particular, deep regret is to have split resources of D into two
halves.

If possible, I want to migrate to D2. And I want to be separated from
Tango. However, some functions are insufficient for Phobos compared with
Tango.
The std.date module is one of the list of dissatisfaction to Phobos.
I summarize my (and some of Japanese users's) opinion following:

- I want to handle it as another thing for the time and the time span.
- I want a more structural class for time operating.
- std.date is a bit buggy...

By these reasons, I made std.time module as the first step of the
contribution for Phobos.