Pkg.fix => pin: decided this is a better name after all.

The biggest issue is that there's a notion of a package being "fixed"
which is different than what Pkg.fix did, although it does cause the
package to be considered "fixed", it's not the only way a package can
be fixed, so it's better to use different terms here.
allow Pkg.clone(pkg) to work [close #4544].

If you do Pkg.clone(pkg) where pkg is a registered package, it is now
the same as doing Pkg.clone(url,pkg) where the url is the registered
url for the package. It's not quite the same as Pkg.add(pkg) followed
by Pkg.checkout(pkg) since it doesn't add pkg to .julia/REQUIRE. This
means that if you do Pkg.release(pkg) after Pkg.clone(pkg) it will
simply remove the package altogether. This may not be the desired
behavior ultimately, but it's what it does right now.
fix a further bug in keyword args in macros caused by 4801de69755a9f5586ac5c0538e3122368d490f7
Extended spdiagm for specifying multiple diagonals
Git: delete old interfaces that were only used by Pkg1.
Pkg.publish: push METADATA even when there are no new versions.

There may still be other metadata changes that need to be pushed.
Pkg docs: fairly complete documentation for the new Pkg [close #4407].
Pkg docs: add section on the requirements format.
Pkg docs: fix RST mistake.

This markup format is so annoyingly brittle.
Pkg docs: copy edits.
Pkg docs: more copy edits.
Pkg.clone(pkg): don't prefetch to cache since we also clone.

It would be good to integrate with the caching mechanism here, but
since this ends up cloning the repo twice, it's no good.
Merge pull request #4547 from cfbaptista/extend_spdiagm

Extension of spdiagm for the specification of multiple diagonals
Fix a couple of doc typos
Fix #4503
Address all issues discussed in #4547
Add test for spdiagm and update docs
Merge branch 'master' of github.com:JuliaLang/julia
update helpdb
"is should" --> "should"
deprecate 2-argument assert function

this is a performance trap since it can lead to unconditionally constructing a message string on every call
Merge pull request #4554 from waldir/patch-1

"is should" --> "should"