Janet 1.21.0

• C functions janet_dobytes and janet_dostring will now enter the event loop if it is enabled.
• Fix hashing regression - hash of negative 0 must be the same as positive 0 since they are equal.
• The flycheck function no longer pollutes the module/cache
• Fix quasiquote bug in compiler
• Disallow use of cancel and resume on fibers scheduled or created with ev/go, as well as the root
  fiber.