Merge pull request #4907 from ivarne/docfix

Fixed broken mpfr.org link
fixed typo in description in manual
Pkg.submit(pkg,[commit]): auto-submit PRs to GitHub-hosted packages.

It's downright magical that this works. Currently this only opens the
URL to create a pull request automatically for you on OS X since the
`open` command does the right thing there. Is there a way to open a
URL on other systems? Windows, Linux?
rename Stat to StatStruct. closes #4670
don't use parseint for uint128 constants in random.jl. fixes #4910
work around for 64-bit checked_mul on 32-bit. ref #4905
Replaced tabs with spaces
Add CodeSpeed and status links to CONTRIBUTING.md.
Fix \ and / for diagonal matrices. Modify tests to check some of the changes. Fix errors in revealed by the test changes.
Provide a header to CONTRIBUTING.md.
Avoid duplicates in sprand
Merge pull request #4899 from JuliaLang/anj/diag

Fix \ and / for diagonal matrices
Re-apply @stevengj's commit e956b3c36f5fea929d5af8cd17b64682f7.

GitHub won't let me download or recover this commit, even though it's
very much publically visible:

https://github.com/JuliaLang/julia/commit/e956b3c36f5fea929d5af8cd17b64682f7

The easiest way to recover from the accidental forced push of master
seems to be to just re-apply this lost commit and carry on. See

https://groups.google.com/forum/#!topic/julia-dev/RE9k7ips7Dc
Add explanation about integer overflow to FAQ
sprand: handle all-zero matrix without error
doc: edits to the FAQ entry on why we use machine integer arithmetic.
doc: slight FAQ edit.
doc: a couple more edits to the FAQ entry on integer arithmetic.
doc: FAQ copy fixes.
Merge pull request #4726 from JuliaLang/teh/sprand

WIP: Avoid duplicates in sprand