Split `distro-build` and `remote-shell` pkgs from the main repository.

`distro-build` is at:
  https://github.com/racket/distro-build
`remote-shell` is at:
  https://github.com/racket/remote-shell
Run distro-build and remote-shell on drdr.
Split `plt-web` from the main repository.

Source for `plt-web` is now available at:
  https://github.com/racket/plt-web
Fix test that used `distro-build`.
Split `slatex` from the main repository.

Source for `slatex` is now available from:
  https://github.com/racket/slatex/
improve a package-dependency error report from `raco setup`
raco pkg update --clone: offer advice on converting directory links
raco pkg {install,update,remove}: add --batch

Adjust defaults for `--deps` and `--multi-clone` to depend on
interactive vs. batch mode.
raco pkg show: add `-l'/`--long', and adjust the default mode

Make `raco pkg show` more readable by default by constraining the
output to 80 characters and adjusting the way some columns print.
optimizer: fix do_make_discarding_sequence

The optimizer converts (car (cons X Y)) to (begin0 X Y) and then reduces
it to (begin Y X) if X is movable.
Check that the movement is safe for space and for continuation captures.
raco pkg update: make `--lookup` and `--clone` work right together

The combination of `--lookup`, `--clone`, and `--catalog` can provide
a one-step path from a snapshot's built implementation of a package to
a repository-linked clone, for example.  In that situation, however,
`raco pkg` will have limited ability to detect that packages
originally drawn from the same repository are consistenly installed as
clones (and we can revisit if it turns out to be an issue).
Split `eopl`, `preprocessor`, and `make` from the repository.

They are available at:
  https://github.com/racket/eopl
  https://github.com/racket/preprocessor
  https://github.com/racket/make
Remove split collections from props.
Remove dependencies on srfis and r6rs.
One more dependency missed.
Fix dependency error.
Make srfi doc reference indirect.
Remove no-longer-needed require.
Split `picturing-programs` and `swindle` from the main repository.

They are available at:
  https://github.com/racket/picturing-programs
  https://github.com/racket/swindle
Remove dependency of "db-doc" on "srfi-doc".