fixing small bug in signal-error: was using future instead of forwarded-future hwne checking for duplicate errbacks. probably wouldnt screw up a whole lot, but its worth fixing.
fixing really annoying bug in alet macro: whenever an error was signalled on a future, alet would re-trigger that error (once for each time wrapped in alet) so a top-level future handler case would fire its error handling forms multiple times (once for the actual error, and once for each child alet form) which caused a lot of mayhem in some of the apps im bulding. this is because alet was forwarding errors from its sub-binding forms to the main collection future, but since the sub-forms are using attach, future-handler-case is able to catch errors with them already...meaning the error was caught and dealt with, but then fired once more by the forwarding process...annoying, and hard to track down, but finally did. now an error triggered deep in the async stack only shows up once. thank god.