Fix mapslice on functions that return scalars.
Merge pull request #2671 from blakejohnson/mapslice-fix

Fix mapslice on functions that return scalars.
Added Mathematica benchmarks
Added missing Mathematica benchmarks and improved speed a bit
Added Mathematica benchmark related stuff to the /test/perf/ Makefile.
Also wrapped some of the test functions in "Compile" to increase speed