Rename racket-extra-test to racket-test-extra.
Split the core racket tests into the "racket-test-core" pkg.

This supports running the core tests on systems which can't run
or don't want to install all the dependencies of the "racket-test"
package.

The "racket-test-core" pkg stil depends on "sandbox-lib" because
the sandbox tests live with the core tests. Hopefully I'll be able
to fix that eventually.
Add configuration for AppVeyor, a Windows CI service.

This configuration will build and test the core of Racket on every
commit. The time constraints are such that only a small portion of
Racket can be built and tested.
Rename to avoid conflict since pkgs is slow.
Use `racket` instead of `scheme`. Fixes dependency issues.
Ignore files here too.
Remove unwanted dependency on mzscheme.

The '#%kernel prop:procedure is the same binding as the mzscheme one.
raco pkg clone: avoid fetching by commit id

A commit id apparently doesn't work in place of a <refexp> in some
versions of Git.
repair a test

The test tried to detect separate evaluations by using the
result of `(current-inexact-milliseconds)`, but a clock's
resolution might not be high enough. Use `(gensym)`, instead.
raco pkg update: better handling of a missing dependency

When updating a linked package whose dependencies have changed,
and when a dependency is missing, then effectively reinstall
the link to get updates as requested by the user.
raco pkg: default `--deps` to `search-ask` in interactive mode

The implemented default for `raco pkg update` actually depended on the
way that a package is installed, and it's difficult to reason about or
to implement the default that is suggested by the documentation.
Meanwhile, `search-ask` seems the most sensible always in interactive
mode (now that we have a way to specify batch mode).
more repairs to stack trace and caching

Fixes problems with d15fda9d6b, but also fixes a problem that
could show up in non-libunwind mode and cause lost frames.
Reduce and fix dependencies for "racket-core-test".

Eventually I'd like to reduce the dependencies further, but this
is enough for now.
Improve AppVeyor configuration.
raco pkg: more information for an ill-formed path error
raco pkg show: mention auto-installed when no non-auto are installed

In the case that packages are only auto-installed in a particular
scope, `raco pkg show` should just say "[none]", instead of adding the
note about auto-installed packages that are not being shown.