Faster JS implementation of rand_mat_mul.

A slightly tweaked rand_mat_mul function that uses B's transpose
to improve sequential memory access during the multiplication. This
speeds up the JS run and, I think, is a fairer comparison with
other languages which call on custom routines to do the multiplication.
Merge pull request #4067 from srikumarks/master

Faster JS implementation of rand_mat_mul.
Add some more float16 related stuff to the docs.
detect msys2 as WINNT
fix issue where we couldn't serialize Base after more aggresive
inlining, apparently because of an anonymous method with a closure in the wrong Base module
fix #4062
Merge branch 'master' of github.com:JuliaLang/julia
Minor combinatorics updates

* Remove extraneous npartitions definitions
* Actually run combinatorics tests
Merge pull request #4068 from JuliaLang/kms/partitions

Minor combinatorics updates
Small updates to NEWS.
More additions to NEWS.
Apply LAPACK patch correctly. (Fix #4069)
Force NEHALEM target when building on OS X Snow Leopard (Fix #4069)
make writedlm work for AbstractVector/Matrix, add corresponding writemime functions