swift234

After testing and measurements, turning on new DSE by default to see whether there is performance improvements or
regression. Local testing reveals a slight performance improvement after replacing the old DSE with the new DSE.
progress tracked in rdar://22873577.

Disable 2 test cases for now so that the build will pass. But I do not want to remove these tests, as they will be useful
to test the new DSE later.

Swift SVN r32267