fix name of function in string-whitespace and remove spurious displayln; Closes PR14679
fix bug in error reporting
fix resource administration in run and launch-many-worlds

the goal is to enable the creation from executables from world and universe programs
separated automatic from manual test so that drdr can run the former
run test in its own eventspace to adjust for change in running worlds and universes
factored out a common pattern in tests
Update PLT sites
fix cross compile on QNX

got broken in 2e284cc78357ccc4a63aae7603682b0344bfc58f
The racket version of libunwind is not compatible with QNX but old-style stacktraces are still working with the default gcc version
Slight change to how drracket handles lexer/colorers, and doc changes to color:text<%>
add slide-pict/center
update dns tests based on change at nwu
Mac OS X PPC: fix dylib paths

Relevant to PR 14694
optimizer: more optimizations for unary operations

Previously, the optimizer simplified the application of some unary functions inside let,
for example (car (let () ... (cons 1 2)) => (let () ... 1). This commit extends this to begin forms,
like (car (begin ... (cons 1 2)) => (begin ... 1).

Also, constant folding and some reductions were only availed in the direct case, for example
(procedure? car) => #t. With this commit these reductions are extended to the expressions
inside let and begin, for example (procedure? (let () (begin ... car))) => (let () (begin ... #t).
RacketCon talks update.
Allow type annotations after for clauses in the for macros.

Cf. GH issue #751.
scribble/srcdoc: add `form-doc`
optimizer: transform ((begin ... proc) x) to (begin ... (proc x))

Currently the optimizer can convert ((let (...) ... proc) x) to
(let (...) ... (proc x)). This is useful especially if proc can be
inlined. Extend this to begin's forms.
optimizer: another ((begin ... proc) x) to (begin ... (proc x))

The tranformation this time applies before optimization of the rator
and complements Gustavo's variant, which applies after optimization of
the rator.
add an optional argument example to ->i docs
optimizer: Remove unused flag added in d14b4a8