Macomber <pgsql@rojoma.com>), as per CL:CLOSE.

  "I've run into a problem with pg-disconnect if something abnormal
   happens to the database connection -- if the database goes away for a
   restart while pg has a connection open, for example.  When this
   happens, pg-disconnect fails, and the socket file descriptor is left
   open (presumably for a finalizer to clean up), also raising a new
   error from the unwind-protect in with-pg-connection.  To guard against
   the possibility, I've added an :abort parameter to pg-disconnect, like
   cl:close has, and made with-pg-connection call it with :abort t if the
   body exits abnormally, in the same way that with-open-file operates.
   When :abort is true, the modified pg-disconnect closes the database
   connection ungracefully, including making the close call abort
   (otherwise, sbcl at keast tries to flush the stream, raising another
   error if the database isn't there anymore)."