library (mostly in opt/c)
Specifically:
- add inlining declaration for ->i helper function
- modernized the opt/c contracts and improved them so that mutually
recursive define-opt/c functions recognize each other instead of
bailing out to the slow path.
- added =/c as an optimized contract
- improve the error message for the between and comparison opt
contracts
- adjust the blame struct so the name is created lazily, since opt/c
contracts just stick a copy o the contract into the thunk that
creates the name and we don't want to run those effects twice if we
can help it.
and documented and adjusted these libraries:
racket/contract/base
racket/contract/exists
racket/contract/parametric (renamed from exists)
racket/contract/region
