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
avoid printf
fix leading example of 2htdp/planetcute to make it a legal
2htdp/bsl program

closes PR 13844
bring down below 102 columns
Cosmetic restructuring of syntax/modcode.

This work is preparation for exporting more functionality from this module.
Renamed variables for clarity and to eliminate shadowing.
Turned lets into defines.
Split a helper function out from get-module-code in syntax/modcode.

The get-module-path function finds the compiled or source file corresponding
to a module; get-module-code reads and compiles the contents of this file.
Exported two more functions from syntax/modcode.

The get-module-path function was described in the previous commit.
The get-metadata-path function constructs the paths used to saved .zo files
and so forth; e.g. PATH/compiled/NAME_rkt.zo.
Add tests for get-module-path.
Added documentation for get-module-path and get-metadata-path.
Fix function names in JSON error messages.
Remove uses of `unstable/debug` from Typed Racket.
BSL doc typos

Hi,

I found two typos in the explanations of lisp-style list accessors.
Patch attached.

Thanks,
s.

Signed-off-by: Matthias Felleisen <matthias@ccs.neu.edu>
Unbreak json tests.
Remove references to `unstable/match` from Typed Racket.
Switch build to the new machine.
Distribute realm.
Synch German string constants with latest.
Post-release version for the v5.3.5 release
Ubuntu machines got upgraded.