Reintroduce nnz and nonzeros as discussed in #6769
Deprecate nfilled for SparseMatrixCSC.
Deprecate nonzeros for StridedArray and BitArray.
Deprecate nnz for StridedArray.
Update documentation for structural nonzeros.
Update NEWS
Use BLAS for pairwise sumabs2 when possible
Only apply the gemv workaround when OpenBLAS is being used.
Rename varzm_pairwise -> sumabs2_pairwise

Also some minor reorganization
Make splice!(::BitVector, ::Integer, ::BitVector) return a Bool

Previously this returned a new BitArray, which was inconsistent with
splice!(::Vector{Bool}, ::Integer, ::Vector{Bool})
Revert "Catch writes to protected memory in mmapped arrays (fix #3434)"

This reverts commit caa4bfa17aeaada0c66f33128e206477842f7eab.
Merge pull request #6978 from lindahua/dh/openblas1

Only apply the gemv workaround when OpenBLAS is being used.
Merge pull request #6963 from JuliaLang/vs/nnz

RFC: Reintroduce nnz and nonzeros
Update style guide to point to FAQ on type parameters
Merge pull request #6979 from JuliaLang/sjk/bitsplice

Make splice!(::BitVector, ::Integer, ::BitVector) return a Bool
Merge pull request #6985 from JuliaLang/kms/doc_param_types

Update style guide to point to FAQ on type parameters
Merge pull request #6974 from JuliaLang/sjk/faster-sumabs2

Use BLAS for pairwise sumabs2 when possible
fix #6977, trying to allocate arrayvar for Array{None}