* module/system/vm/traps.scm (new-disabled-trap): Don't manipulate the
VM trace level in the enable and disable handlers. Unfortunately, this
makes traps not work unless you enable hooks, but given that
vm_dispatch_hook has to set trace-level to 0, there needs to be an
object with a broader view of what traps are enabled. That object is
the hook state.
* module/system/vm/trap-state.scm (trap-state->trace-level): New
procedure.
(with-default-trap-handler): Add an optional trap-state argument. Now
makes sure that the vm-trace-level is set appropriately during the
execution of the thunk, allowing for breakpoints from recursive
prompts.
* module/system/vm/trap-state.scm: New file, tracks a VM-specific set of
traps.
* module/Makefile.am: Add trap-state.scm.
* module/system/repl/error-handling.scm: While in a with-error-handling
block, bind a default trap handler that invokes a recursive prompt.
* module/system/repl/command.scm: Add a `break' repl meta-command.
