Fix typo in GUI type
extend 'open collection path' menu item to support local files,

when the dialog's content starts with an open quote, ala a require
switch `gracket`-based DrDr tests to `raco test -m --fresh-user`

Various GUI (especially DrRacket) tests have used `(gracket *)` as
a signal that the tests must be serialized, but those tests can run
concurrently if run with a different "home" directory (as determined
by the `PLTUSERHOME` environment variable).

Change those test to use `raco test -m --fresh-user`, instead,
which runs the test with a fresh home directory.
meta/tests/unix-installer: disable for DrDr

The test is meant to be run manually at release time.
scribble: recognize 'exact-chars even when a style name is #f

Patch from Tero Hasu.
allow `expand` on cross-phase-persistent modules

Previoulsy, `expand` mode explicitly disallowed cross-phase declaration
in commit 2e652fc2b3. I'm not sure why, and that commit has no test
case that fails when the restriction is removed, so my best guess is
that it was a debugging strategy that I forgot to undo.
fix switch of `gracket`-based DrDr tests

Forgot the `*`, so the tests were not run.
fix problem with `(continuation-marks <thread>)`

A thread can be swapped out while it's in transition between a
mandling of the mark-stack position and recovering from C-stack
overflow. Fix up that case.
fix `expand` on a `module` containing a `#%declare` form
fix `expand` on a `module` containing lifts from expression

Another attempt at the bug that b95baa1d25 was intended to fix.
racket/port: enable buffering for `peeking-input-port`
increase timeout for "teachpack.rkt" test

The test now runs concurrently with other GUI tests, so it competes
more for various resources.
check-satisfied: documentation for both htdp-langs and test-engine
check-satisfied: added feature to the htdp languages
check-satisfied: added tests for test success and failure; todo (in general): error message checks
check-satisfied: the basic functionality, the display in repl and test suite gui, plus the communication among these modules; missing: language constant
how to add a new check- feature to test-engine
clean up requires
clean up doc

it is still worrisome that I am documenting something from here that students should never, ever see
Export editor stream base classes in TR GUI