raco setup: add package-dependency checking

The new `--no-pkg-deps' or `-K' flag skips the check.

If a module in package X refers to a module in package Y, check that
package X declares a dependency on Y.  Note that package X must
specifically depend on Y --- not another package that at the moment
happens to declare a dependency on Y.

A new "base" package represents the content of the core (so that, if
the core shrinks, a new "base2" can represent the smaller core).
Most every package now needs a dependency on "base".

Sometimes, it makes sense for X to access Y when X declares a
dependency on Z, because Z promises to always depend on Y.  For
example, the "gui" package is defined to combne "gui-lib" and
"gui-doc", so it's appropriate to use the modules of "gui-lib" when
depending on "gui". A package's "info.rkt" can therefore define
`implies' as a subset of the dependencies listed in `deps', which
means that depending on the package implies a dependency on the listed
packages. (It's even possible for packages to mutually imply each
other, which is why the dependency checking code ends up with a
union-find.)

Dependency checking distinguishes between run-time dependencies and
build-time dependencies: anything listed in a ".dep" file is a build
dependency, at least. To imply a run-time dependency, a reference must
appear in a bytecode file's imports, and not in a subdirectory or
submodule that would be pruned for a binary package.

The `--fix-pkg-deps' flag attempts to automatically fix package
dependency declarations (i.e., modify a package's "info.rkt" file)
based on inferred dependencies.

original commit: 04d5d9bd55

racket/lib/collects/setup/option-sig.rkt

@@ -22,6 +22,8 @@
      avoid-main-installation
      make-tidy
      make-doc-index
+     check-dependencies
+     fix-dependencies
      call-install
      call-post-install
      pause-on-errors