[spec-S32-Temporal] move Duration to the top, making it more generic, while it still delegates to Gregorian::Duration if you use anything different than :tai in the constructor
[spec-S32-Temporal] move Duration to the top, making it more generic, while it still delegates to Gregorian::Duration if you use anything different than :tai in the constructor

git-svn-id: 53605643c415f7495558be95614cf14171f1db78@28215 c213334d-75ef-0310-aa23-eaa082d1ae64

prammer/specs,prammer/specs,prammer/specs,tokuhirom/specs,tokuhirom/specs,perl6/specs,perl6/specs,tokuhirom/specs