setup/pkg-deps: fix "racket" mapping

I'm unable to construct a test that exposes the problem, but fix the
"type" on the dependency list for the special "racket" package.
fix declaration for non-places, non+futures build
raco {pkg,planet}: exit with non-0 status for bad sub-command
raco pkg: check for conflicting docs, executables, etc.

Unfortunately, many existing packages rely on the fact that documentation-name
conflicts do not cause trouble when a package is installed in user scope
(because the documentation in that case is rendered with the package).
So, flag conflicts only for installation scope by default, but add a
`--strict-doc-conflicts` flag for strict checking even for user scope.
meta/pkg-build: handle dependency cycles
fix encoding of CMN in ARM JIT

It looks like bits 12 through 15 of the ARM encoding for CMN
should be 0s, not 1s, although many processors don't care.
add float behavior for margin-note* CSS
restrict float behavior to narrow screens
sync "base" package version
clarify pkg docs on "racket" dependency

Encourange a depedency on "base", instead.
clarify that document names are meant to be globally unique