Before this commit, the files that are loaded during expansion
were discarded when an error during expansion occurs. This commit
saves them: unless the program is something like
(begin-for-syntax (kill-thread (current-thread)))
the handling that deals with that kind of situation (as opposed
to just an exception being raised) doesn't try to save them
Do not merge to 5.3.2: this bug isn't serious and the new code
is not as well tested as the old
Things should now generally be set up to work better --
for example online check syntax is smarter now about
what happens when switching tabs/frames and this also
makes it easier to add new ways for a window to become
dirty (that is, for it to be known that it needs to
be recompiled)
can get "stale" and cause DrRacket to deadlock (this commit just sets
up some stuff to make one fix possible, but that fix doesn't seem to
be working, so the actual fix is disabled (see comment in commit))
specifically, when drracket kills the thread that is expanding/transforming
the program, first print out its stack trace. that way, if it is stuck
somewhere, maybe we'll get a clue as to where
being edited in DrRacket (via places)
Added an API to let tools have access to that
information (and compute more stuff)
Used that to make an online version of Check Syntax
which led to a separately callable Check Syntax API.
