Fix TR treatment of parent row in class types

This bug manifested in having extraneous class
members in a type for a class whose superclass
expression was a mixin application.
Fix Guide typo

Please merge to v6.1.1
Fix TR docs on #:implements in Class types

Please merge to v6.1.1
raco test: fix `-l`
raco test: show more of stderr on failure
syntax-color/lexer-contract: make random-test failure declare itself

Random tests that are implciitly injected into a program should
declare themselves as such when they fail. Otherwise, random
crashes are really confusing.
syntax-color/racket-lexer: fix problem with unclosed "| "

... where the whitespace character after "|" is non-ASCII.

This bug was found by random testing in `syntax-color/lexer-contract`.
racket/udp: adjust receive into a zero-sized buffer

The OS doesn't necessarily react to a zero-sized buffer the way
that `udp-receive!` is supposed to work, so provide only a
non-zero-sized buffer to the OS.
correct `register-finalizer` docs by clarifying prohibitions
pkg manage docs: clairfy in overview that a git repo tag is allowed
Inside Racket: document Windows-specific treatement of "UTF-16"
openssl: fix `ssl-load-default-verify-sources!` for Win64

Closes PR 14784

Merge to v6.1.1
Add a test for generating GUI contracts for TR
Use a new approach to generating Name contracts

This handles contract generation for recursive or
mutually recursive Name types in the static contract
framework.

Instead of just generating recursive-sc static contracts,
it memoizes the recursive contract within a single
type->contract call by indirecting through a table.

When static contracts are instantiated, the table is
consulted for computing contract kind information and for
generating the actual contracts for the recursive names.
Greatly reduce size of class static contracts.

This helps generate contracts for GUI classes using less
time and memory.
Add contracts and omit an unused definition
make to-draw (alt-kw) error messages more correct, see test for flaws; closes PR 14781

please merge with 6.1.1
improve error message