stride behaves differently on subarrays and arrays

[dmbates]

I encountered this when solving a linear system of equations using LAPACK. Functions like Base.LinAlg.LAPACK.potrs! evaluate stride(B,2) where B is the right hand side. If B is, say, an Array{Float64,1}, this evaluates tolength(B)but ifBis aSubArray{Float64,1}it throws aBoundsError`.

I feel the best thing to do is to change the stride method for SubArray to match the behavior of that for Array but I guess we could instead change the logic in the LAPACK functions.

[timholy]

Agreed. I'd noticed this myself, but didn't get around to fixing it. Given the impending 0.2 release, I've done this as a PR: #4416.