plt-racket 6.1.1

Closes #34754.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
plt-racket: update 6.1.1 bottle.
Update libbpg to 0.9.1

The author has thankfully included some of the inreplace Makefile
fixes in the upstream 0.9.1 release's Makefile.
libbpg: add 0.9.1 bottle.