Add the Java 6 java.text.spi and java.util.spi interfaces.

We don't currently use these, and don't necessarily plan to. Full support
would have a run-time cost, and it's not obvious that it would be particularly
useful.

Code search can't actually find any users of this stuff in the wild outside
of the various VM implementations and their test suites.

Bug: 2497395
Change-Id: Ie25aef73ece6d1fd169fdcb7b2f847761d77914d
11 files changed