REPL: improve "using" completion

Allows to complete when using followed by
comma-separated lists.
make inlining heuristic more conservative
Merge pull request #3796 from JuliaLang/jn/callmore

more inlining
update type of code_lowered to Callable instead of Function
repl: bind history prefix search to pg up/dn (#6377)
repl: simpler history file search code
Change distclean target to distcleanall
fix readdlm regression. fixes #6376

eltype checks for readdlm return values.
REPLCompletions: simplify complete_symbol
Improve REPL completion after using keyword

also detect "import" keyword
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
readdlm handle CRLF line ending with quoted column
Add uncommitted blob to update linalg tests (whoops)
Break up the linalg1 test suite further
Fix REPL completion display for multiline inputs
Merge pull request #6332 from JuliaLang/anj/make

Change distclean target to distcleanall
initial stata support in benchmarks