Log message:
Update to Racket 5.0.1

Continuation barriers now block only downward continuation jumps
 and allow escapes through full continuations
Changed internal-definition handling to allow expressions mixed
 with definitions
Added support for subprocesses as new process groups
Added support for best-effort termination of subprocess by a
 custodian
Added flreal-part, flimag-part, make-flrectangular, and unsafe
 variants
Added fl->eact-integer, fl->fx, and unsafe-fl->fx
Added #:async-apply option to _fun
Added chaperone-evt
Added identifier-prune-to-source-module
Changed apply binding to enable lower-level optimizations
Upgraded to libffi 3.0.9+

Log message:
Mark CONFLICTS with obsolated drscheme and mzscheme,
and racket{,-textual} each other.

Log message:
Import Racket 5.0 as lang/racket.
Import textual Racket version as lang/racket-textual.

Racket (formerly PLT Scheme) is a specific dialect of the Lisp
language based on the Scheme branch of the Lisp family.