Merge branch 'patch-3' of git://github.com/hkdobrev/core into 3.4/feature/arr_get-work-with-arrayaccess-and-null-values

Merged Merge branch 'patch-3' of git://github.com/hkdobrev/core into
3.4/feature/arr_get-work-with-arrayaccess-and-null-values with
modifications:

- Passing `NULL` as first argument would NOT return the default.
Also removed related tests

- Passing something else than `array` or instance of ArrayAccess
would NOT throw an exception. We leave that on the PHP runtime
to take care instead. Also removed related tests.

- Removed HHVM workaround message, HHVM is now compatible with PHP
starting HHVM v.3.3.0

Conflicts:
	classes/Kohana/Arr.php