Add ICU DateTimePatternGenerator API to HPHP

Summary: Added a PHP API for the C++ icu::DateTimePatternGenerator. I tried to follow the conventions of the other ICU PHP classes. When there is an error, we throw an exception. The error message/code can be accessed through getErrorMessage/getErrorCode. Like many other Intl classes, the way to create a DatePatternGenerator is through a static method, createInstance or createEmptyInstance.

Reviewed By: @bgertzfield

Differential Revision: D1691412
Support run extension's test case with hphp/test/run

Summary: Currently built-in extension's unit test are located in hhvm codebase, but the opensourced
extension mostly use phpunit, but I
think use `hphp/test/run` to test makes it more consistent, it can be the standard way
to do unit test of HHVM extension.

Now hhvm-dev package should contain hphp/test/run,
after running `hphpize`,  `run` will copied to extension dir and renamed to `run-test`.

User can run `make test` to run tests under folder `test`, currently
it can only be in `test` folder
Closes https://github.com/facebook/hhvm/pull/4358

Reviewed By: @​svcscm

Differential Revision: D1709443

Pulled By: @fredemmott