New Racket version 5.3.4.7.
added stepper-complete string constant
raco setup: add --doc-index; raco pkg: use --doc-index

This combination of changes moves the decision about rebuilding
"scribblings/main" and "scribblings/main/user" to `raco setup',
which is in a better position to know whether documentation should
be built at all.
Adding summary mode, quiet program mode and changing tests/eli-tester to cooperate so it adds useful information in summary mode
Clean up struct: and disallow unsupported options

Related to PR 13562
use correct value for (processor-count) on QNX
fix bytecode validator bug

If a function is bound by a `letrec' (or internal definition)
that cannot be simplified to `let' or lifted to a constant or
top-/module-level function, and if the `letrec' binding is used in
a non-application position, and if the function has in its closure
a typed binding (i.e., boxed, fixnum, flonum, or extflonum),
then the validator was incorrectly rejecting the function's
bytecode --- because the validator didn't distinguish between typed
arguments and typed closure content.

File under "surprised that we didn't hit this one earlier".
raco setup: allow foreign-lib and man-page installation

This change hopefully fills out the things that a distribution
can do and that packages should be able to extend.
some random tests to try to stress the immutable hash table implementation
Fix docs for Opaque

Closes PR 13531
Fix race condition in `delay/thread'.

There's mutual dependence between promises and their threads. This may
cause a thread to start running before its promise is fully initialized,
in which case it will be `#<undefined>', which causes errors down the road.

This was the cause of an intermittent failure in the TR test harness.
Refactor and add purpose statements/contracts
Fix printing of tc-any-results in type errors.

In the long run, these error messages should get
simplified so that this printing is not necessary.

Closes PR 13577 and PR 13526
add missing require
remove some misleading uses of 'else' from Redex
minor clarification of properties and datum->syntax
more else -> _ conversions
Synch German string constants with latest.
add error checking
redex: fix unify coverage tests

expect `_' from match-a-pattern, instead of `else'