Remove without-interrupts from runtime/process.scm.

Remove without-interrupts from runtime/process.scm.

Serial access to a subprocess is the responsibility of the user.  Thus
subprocess-i/o-port and close-subprocess-i/o do not need without-
interrupts to implement it.

Closing a port twice should not signal an error, so subprocess-delete
and close-subprocess-i/o do not need even without-interruption.
However they should close the port before clearing the subprocess
slot, else an abort could drop the port and it's channels may not be
closed for an arbitrarily long time.

Status sync could miss changes and subprocess-i/o-port and
make-subprocess could drop a subprocess or port if aborted mid-stride.
They now use without-interruption.