This keyword argument was added in SBCL in 2010 and is used to pass
ABORT to CL:CLOSE.
The absence of this would obviously cause errors when code expects
this to be available. For example, this happens in usocket's
SOCKET-CONNECT and would cause several errors in their test suite
with obscure error messages like
Wrong number of arguments passed to function #<compiled-function 0000000003562e80>.
This is untested on Windows.
de661f580a