guard a call to invalidate-bitmap-cache in
check syntax so it only happens when something
would draw differently
web page: videos link and other small changes
fix bug in commit 4c4161ce2bb6ca3e81282d0df27b916349b64a84
bring back the syncheck:add-rename-menu method in a way
that preserves backwards compatibility for the
drracket/check-syntax library
fix some bugs in union-find

(thanks to random testing)
unbreak drr
adjust check syntax so it highlights all identifiers with the same
binding site (with a green/yellow bubble) when the mouse moves over
any one of them

This change comes about because of the recent fixes to the
interactivity wrt to the rename menu. Basically, in order to fix the
bug (but still preserve the interactivity optimization), check syntax
changed from sending the information "here is a place to offer a
rename for these identifiers" to "here is a set of identifiers that
are all free-identifier=?" (the difference being that the latter does
not imply you got them all (which enables the optimization) and that
the information is slightly less rename-menu specific (which enables
the change in this commit))
Rackety
make the online check syntax error message font
size match the user's preferred font size

(useful in a classroom / talk setting)
fix close paren correction code
Fix typo.
More: clarify how to use DrRacket instead of plain `racket'
more close paren adjustment repairs
v5.3.2 installers info
Add types for imaginary numbers and fix type of exact? and inexact?.