add some missing pref items docs
add a column-width guide; defaults to 102 characters, but disabled
added history not about column width guide
fix `hash-copy' on weak hash tables

Closes PR 13838
setup/cm: fix some dependency tracking on deleted files

Based on a report and patch from Tobias Hammer.
Add an equality checking argument to `member`
Update TR base environment
Remove `memq`, `memv`, `member` from #%kernel

These are now implmented purely in Racket on all
platforms.
Fix build. Forgot to add this file in c305dba.

Apologies to any future git bisect-ers
Fix cstartup and the build.

Somehow this got messed up in c305dba though I'm
not sure how.
redex: add `where-make-prefix-pict' and `where-combine' for typesetting
raco setup: fix for bootstrap
New Racket version 5.3.4.12.
add docs for text:column-guide-mixin and text:column-guide<%>
avoid ugly nested conds

Thanks, Laurent!
Protect against invalid package sources
Language-level demodularizer.
Fix typos and shadowed names in class docs
Fix collects for setup with single-collect package

Before this commit, raco would try to setup each
subdirectory inside of a single collection package
as separate collects.
Games:Remove-mzlib-unitsig-and-cleanup
-Remove all instances of mzlib/unitsig in favor of racket/unit
-Prefer /infer forms.
-move to #lang racket from (module ... racket forms
in the modified games and files.
-remove some lingering scheme imports.
-update documentation

-Paint-by-Numbers:
-move to racket/unit
-update solution and problem gen files to generate using racket/unit
-regen the problem and solution sets using racket/unit