fix bug in online check syntax
add support for firing up a REPL to poke at DrRacket
add the ability to load in new mixins to DrRacket's
various get/extend:extend functions
fix interference of unboxing inference for different arguments
Support SO_REUSEADDR on (udp-bind!), for multicast use.
UDP Multicast primitives and documentation.
Make xform build step work in Windows builds
bump version number
reference: adjust docs for UDP multicast

Minor style changes to better match the rest of the docs,
plus "HISTORY.txt" entry.
reference: fix grammar for cross-phase expressions
doc search: fix mismatch between generator and renderer

This change revisits commit eb7fa6f066. I think the problem
is not in the rendering of index entries but on the generation
side. The generator was converting Xexprs to strings, except
that strings were left as-is, which is inconsistent. So,
I've reverted commit eb7fa6f066 and fixed the generator.
Add #:lang and input-program inputs to make-base-eval and friends.

This commit extends make-base-eval, make-base-eval-factory, and
make-eval-factory with an #:eval and input-program inputs so that
these functions are more like racket/sandbox make-evaluator.
fix `udp-bind!' test
test-equal->test for better drdr source loc info
Fixes PR13655
Fixing PR13657
A few links
fix non-terminal reference
get a better name for certain contract error messages

related to PR 13665
fix bad call to raise-argument-error and use ->i instead of ->d
for the mixin contracts