If a file or directory delete fails, try adjusting the file or directory
permissions to allow writes, then try deleting again. This process should
provide a more Unix-like experience and make programs behave more
consistently.
A new `current-force-delete-permissions` parameter provides access to
the raw native behavior.
If the slow path has to be taken because the number of
list elements is greater than the stack size, then the
old implementation would copy all the arguments --- which
still might be too much for the available stack space.
Avoid that copy.
Also, add pad word to the end of the stack to help detect
overflow.
For example, reduce (begin x (error 'e) y) ==> (begin x (error 'e)) and
(f (error 'e) y ) ==> (begin f (error 'e)).
Also, reduce (if (error 'e) x y) ==> (error 'e) and propagate the type information
and clocks when only one branch produce an error.
This required moving some tests to "racket-test", and putting them
in modules that use `rackunit`. Also, some uses of rackunit were
removed and switched to more primitive systems. Some improvements
here, particularly in "foreign-test.rktl", would still be good,
but everything passes at the moment.
The test tried to detect separate evaluations by using the
result of `(current-inexact-milliseconds)`, but a clock's
resolution might not be high enough. Use `(gensym)`, instead.
This supports running the core tests on systems which can't run
or don't want to install all the dependencies of the "racket-test"
package.
The "racket-test-core" pkg stil depends on "sandbox-lib" because
the sandbox tests live with the core tests. Hopefully I'll be able
to fix that eventually.
