fix docs on `case'

The Guide was was out-of-date in several ways, and the Reference
didn't describe the dispatch-time guarantee.
Fix subtyping for Negative-Single-Flonum.
Filters for comparisons with inifinity.
Add examples of function types with keyword arguments.
Add an example for `local-require`
Add doc subforms for keyword types
Add link to the syntax of the @-reader.

Also defines the "@-form" term in the @-syntax section due to its
frequency.

Closes PR-12589.
various 0-sized image repairs

closes PR 13540
make read-csv-file/rows available in BSL; closes PR 13542
Conditionally link to the SRFI docs on docs.racket-lang.org when rendering PDFs.

Closes PR 11804.
minor clarifications of the docs (that would have helped me
understand some of the details better).
add docs to address how image equality, rounding, and alpha values
can conspire to confuse

closes PR 13541
fix documentation errors

closes PR 13543
Make mutable lists be sequences.
Move eopl language to Racket.

- sllgen.rkt - use begin-for-syntax+define-syntax instead of
  define-syntax-set.
- eopl.scrbl - rewrite *3-columns so that it no longer errors when 3
  doesn't divide the number of reprovided lang forms.
- Removal of mzscheme and mzlib requires.
- Updated docs.
Newlines at EOFs scan.
Some style things.
racket/draw win32: Pango patch

Closes PR 13513
Revert "racket/draw win32: work around a Pango bug"

This reverts commit 8f9606007fee4caece23214b0b20dc36a3a7c010.

Figured out how to compile and fix Pango after all.
add a contract on the interaction between the module-lexer and the
lexers it defers to

also, remove the checks in color.rkt in the framework (they are not
all covered by the added contract, but they mostly are and when they
aren't, most of those times are using the heavily tested racket-lexer)