OK. This was re-written already with multi-processing in mind.
uerror.scm:62: (set-interrupt-enables! interrupt-enables)
+ Caller: handler installed by define-error-handler.
uerror.scm:75: (set-interrupt-enables! interrupt-enables)
+ Caller: handler installed by define-low-level-handler.
uerror.scm:418: (set-interrupt-enables! interrupt-enables)
+ Caller: default handler in error-handler-vector.
+
+ OK. These all just restore the pre-interrupt mask.
unpars.scm:515: (if (with-absolutely-no-interrupts