fix readdlm regression. fixes #6376

eltype checks for readdlm return values.
fix #6384, promotion loop in colon
Don't export concrete Factorizations by default.

There seems little need to have matrix factorization objects exported by
default and cluttering up the default namespace. Most users should never
need to construct them explicitly with constructors, and it should be
sufficient for most users to work with them as possible return types of
various operations.
Also don't export Schur factorization.

- Removal of matrix factorizations from Base namespace noted in NEWS.md
- Also minor formatting fixes to NEWS.md
Merge pull request #6381 from tanmaykm/readcsv

fix readdlm regression. fixes #6376
Add uncommitted blob to update linalg tests (whoops)
Use julia parser in completion

Replaces the heuristic machinery for determining whether
completion is attempted from within a string, a command etc.
with the julia parser.