Fix the TR fix in efd482c30ff80f

My fix had just patched over a contract violation in a different
function. This commit fixes the root of the problem.
Unbreak the build on FreeBSD 10.

isnan expands into a use of a function called _Generic.

Tell xform not to worry about it.
fix `peek` implementation in R6RS input ports

The peek operation must not block, otherwise the port behaves
badly for `sync`.

Based on a bug report from Brett Stahlman.
fix "r6rs-test" dependency declaration
redex: favor recursive rules above the bound
Add more typed bindings for framework and for GUI
Fix type for text:line-numbers-mixin
redex: fix recursive calls to use premises clauses
avoid stack-overflow in scheduler-triggered foreign calls

While a foreigh call is normally guarded by a check on the amount
of available stack space, a callbacks triggered by the
scheduler will first put Racket in no-stack-overflow mode, and
then it's too late to check stack space before making further
foreign calls. With Cocoa, there's some chance that the process
will run out of space. Avoid the mismatch by checking the stack
availability at the start of a scheduler iteration.
Change RacketCon title and abstract.
RacketCon Logistics info.
Fix to the RacketCon web page source.

Should have been included in the previous commit.
Add `raco pkg archive`.

This creates a catalog from the specified currently-installed
packages. The catalog can then be used to replicate some or
all of the currently-installed packages in another installation
or other context.

Also extend `pkg/command` so that `#:multi` is useful.
improve contract-stronger and related things

Specifically, add a mechanism so that contract combinators
can accumulate contracts on a value (instead just storing
only one) and then use that in instanceof/c to avoid
putting contracts on values more often.

Also, fill in better contract-stronger implementations in
some of the combinators
docs and tests related to a0880f740
Fix test failure in `archive` tests.
Those commits can change the blame assignment in
incorrect ways

This reverts commit 0aee13bf224960d5c7d93815170b9a20ed41d08f.
This reverts commit a0880f74037e1e3fe8d2f1d10f621428e6ad74dc.
fix bug in ->i expansion when the name ctc is used in certain ways
add a proper stronger implementation based for recursive-contract

Following _Subtyping Recursive Types_ by Roberto M. Amadio and Luca Cardelli
Synch German string constants with latest.