Improve performance of newSmallArray#
- Hoists part of the condition outside of the initialization loop in stg_newSmallArrayzh.
- Annotates one of the unlikely branches as unlikely, also in stg_newSmallArrayzh.
- Adds a couple of annotations to allocateMightFail indicating which branches are likely to be taken.
Together this gives about 5% improvement.
Signed-off-by: Michal Terepeta <firstname.lastname@example.org>