exp/locale/collate: added indices to builder for reusing blocks between locales.
Refactored build + buildTrie into build + buildOrdering.
Note that since the tailoring code is not checked in yet, all tailorings are identical
to root.  The table therefore should not and does not grow at this point.

R=r
CC=golang-dev
https://golang.org/cl/6500087
3 files changed