new unix bitmaps for redex tests to sate drdr

thanks, Jay
fix UDP improvement for Windows
disable this file in 'raco test'
Use gl-config% multisample size as an upper bound instead of a lower bound
db: stick to ASCII for pg generated names
Change prose about RacketCon videos.
Added support for core OpenGL profiles in Linux (see `set-legacy?`)
use a new strategy for computing the baseline for the various beside functions

Instead of just taking the maximum  value of any of the baselines in the
beside case, look for the largest difference between the bottom and
the baseline and take the location of that image's baseline as the combined
baseline. If the differences are equal, take the one that is furthest away
from the top

closes PR 14760
fix bug in 144fdb2a
move the module browser into the drracket-tool-lib pkg
for lighter-weight reuse
Add more XSync to clear the queue to avoid crashes with repeated use
fix syntax error check in 'bitmap'

closes PR 14763
add show-content as a simple way to get started with the
drracket/check-syntax library
require only original-enough? syntax for require annotations
make 2htdp/image's equality function ignore baselines

also some Rackety and spelling

related to PR 14760
fix editing error

closes PR 14764
don't hide the tooltip frame before moving it under linux
Add type tooltip information in TR modules

This lets DrRacket show types for expressions that
are typechecked.
Added `get-current-gl-context`, tests (also for `make-gl-bitmap`), and docs
fix rendering of metafunctions that use ∪, ∨, etc in the range contract