Make the occurrence analyser propagate info into non-rec RHSs

See Note [Use one-shot info] in OccurAnal, second bullet.

This one change produced some useful wins

        Program           Size    Allocs   Runtime   Elapsed  TotalMem
--------------------------------------------------------------------------------
            hpg          +0.0%     -2.4%     -4.3%     -4.8%     +0.0%
   k-nucleotide          -0.0%     -7.1%     -0.3%     -0.3%     +0.0%
         sphere          +0.0%     -5.6%      0.08      0.08     +0.0%
--------------------------------------------------------------------------------
            Min          -0.1%     -7.1%    -10.7%    -11.0%    -33.3%
            Max          +0.1%     +0.2%    +15.4%    +15.4%     +1.7%
 Geometric Mean          +0.0%     -0.2%     -0.1%     -0.2%     -0.7%